I'm starting to see more of what's going on now. 
You need to love yourself. The reason this insecurity hasn't gone away no matter how much you know about it, no matter how much you know what's going on, what you think stems your insecurity etc. even on the meta level is because fundamentally you're using the temporary external environment (your boyfriend/people) to validate your worth. And I'm here to tell you that this will NEVER EVER work. It will only keep you spinning your wheels as you have been all these years, it's like watching a marathon on Netflix but then after you've watched all the episodes you're left with this empty feeling/void because it never made you full and leaves you wanting more, even if they had 60 seasons eventually there would be none. It's LIMITED. the only permanent solution is to create love for yourself. 
A person to help with this is someone like Matt Kahn He's absolutely amazing when it comes to teaching you how to love yourself and finding your own value. 
The next time you find yourself having these emotions again, love yourself. Love the one who is angry. Love the one who doesn't feel attractive. Love the one who is insecure. Love the one who doesn't like herself. Love the one who doesn't feel good enough. Just sit there and try to love yourself to death, and you might not like being loved so much, but do it anyway, because what you're feeling you're healing, and over the weeks and months it will slowly start to get out of your system.
Create an unconditional love for yourself. We all love you, but we can only get so far. The love ultimately has to come from you.
 

It sounds like contingent happiness. (Happiness is love, awareness, consciousness, infinite being). The contingency looks like; have her, I’m happy. Don’t have her; I’m not happy. I’m not suggesting this is easy, it’s not. It takes experience, heartbreak & ‘rebuilding’ from heartbreak. But the light at the end of the tunnel is that happiness isn’t something you have, which you could lose… because it’s the true nature of what you are… but thoughts, or, the mind, kind of hijacks the happiness / love by projecting it onto the having or not having of someone or something, or of things going or not going your way. It is rough, but it does get better & better the more one experiences, and learns to let go of discordant thoughts, namely about oneself. 
There are ways to go about this….
Meditation. Then there isn’t attachment, or as much attachment, to the thoughts. Then when a thought like “I might lose her” arises, there is still some space around the thought, and that space is happiness / love. So the thought isn’t so convincing, and the ‘loss’ doesn’t seem so detrimental or threatening. This is completely innocent and pretty much, again, requires experience to learn and realize. Everyone get’s into this place via forgetting they are the happiness / love. When you ‘have it’, it seems like it’s arising from an outside source. Meditation is most helpful is clearing the mind, such that it becomes clearer happiness / love arises within you, and inevitably, is you. If you can hear this - what you want to happiness / love, not per se, any one person or relationship. Again, there’s a learning curve. Don’t ‘beat up’ on yourself. Please don’t take / use what I’m saying in that light. 
Another way to shift perspective and thus feeling, is entertaining the perspective that you never ‘have’ her to begin with, such that you could ‘lose’ her. She’s not a possession. She’s not something you need, to be happy, to feel the love that is / you are. It’s likely the thought arises.. “then what do I need to do to know and feel this happiness / love that I am?”. And that is the big paradox which makes youthful heartbreak so rough - there isn’t anything you can do per se… but if you let go of any thoughts or beliefs about yourself to the contrary, the happiness / love rises of it’s own accord, effortlessly. 
Another way is to shift what you’re focused on. Not per se at the time of argument or of a break up, but generally, kinda, all the time… putting more ‘happiness / love stock’ in the thrill & wonder of creating the life you most deeply desire to create - that being with or without a relationship, a significant other, or sex, etc. I am not saying you shouldn’t desire or make efforts to have relationships, sex, etc. I am saying ‘your’ happiness is less contingent on someone else than it seems, when we’re young. No offense. Again, it’s innocent. Generally, people who do ‘find’ that happiness love, and it’s from a relationship, end up feeling there must be more. It’s not satisfying. It is at first, but not in the long run. In a way all roads lead to self realization and the wonder of consciously creating. 
Arguably the most important factor is letting go. Which again, takes experience. By letting go I mean… when you’re already upset, angry, heartbroken, concerned, worried, frustrated, etc, etc… all you really want is to feel better. So we think and ‘make moves’ attempting to feel better. But we can’t, as Esther Hicks says, “get from there to there”. You can’t get from anger to passionate creating for example, without letting go and feeling contentment along the way. One must let go, or, empty the cup, so that it can then be filled with the goodness one is. Then it just gets clearer and clearer happiness / love is ever present, and ever available, without contingencies. 
Also… the current interpretation might be confusing to you, but you might be missing that the confusion, and likely frustration, arises from the interpretation. You might interpret that you need validation and are insecure. But it’s possible that isn’t actuality true about you at all. It’s possible that complimentary words and kindness from people are more of a break from thoughts which don’t feel good. Thoughts about yourself perhaps. Without thoughts / beliefs about yourself that don’t feel good, there is little need, desire for, or even interest in feeling better from compliments or validation from outside yourself. Again, takes experience, consideration, contemplation, expression, and meditation is most helpful.
Might be helpful to express how you feel, understand why your parents or influential people around you act & behave(d) as they did / do. Often when you see they’re doing their best, a lot which you might have believed to be about you is seen to be outward projection from them, which had nothing to do with you. I mean, you might have caught the brunt of it, it might have been anywhere from unpleasant to traumatic, but the freedom is realizing it’s not your fault, and ultimately understanding & forgiveness of others, is the ultimate freedom for you.