The best way I’ve found to do this is to a) own your insecurities, don’t blame them on other people, and b) talk openly and honestly about them, don’t try to hide insecurity behind anything else.
The reality here is that insecurities are bigger than your relationship, you will carry them with you to your next girlfriend. Hiding from them just kicks the can down the road. If you can fix your insecurities, even at the cost of your relationship, you should take the trade, because in the long run you’ll be much much happier.
Insecurities are rough because they don’t directly cause you any distress. You feel like you’re acting normally, it’s everybody else that’s screwed up. The girlfriend who just won’t respect you, your friends who you think are abusing you. Sometimes this is true, other times it’s just you.
So what you need to do is look for discrepancies in how you are acting, or how your SO is acting. Say she said something that you found really hurtful. What you need to do is ask her why she said that. She’s going to come up with a rationale for her behavior. That rationale is either going to carry the ring of truth, or it will feel hollow.
If it feels truthful then you have something you need to examine. What caused you to act in the way that made your girlfriend say mean and hurtful things to you? Dig deep and seriously consider the idea that you might be wrong. You can ask follow up with your girlfriend in the frame of she’s helping you to understand yourself.
If it rings hollow than you need to start examining her behavior, looking for her insecurities. Again, you can ask her about them, but you need to be delicate because working with insecurity causes people to blow up. Your best bet is to keep it light-hearted and short. Ask simple questions, and be happy with the first answer. Don’t make a big deal out of anything.
Chances are both of you are insecure about something. If a disagreement ever escalates to an argument then you can be guaranteed that both parties have a latent insecurity that may or may not be dealt with.
Once you’ve discovered an insecurity, then you need to own it. Just tell people in random conversation that you get seriously jealous every time X happens. Like it’s the most natural thing in the world. Hiding it only makes it worse. The nice thing about this is that talking about it with others allows them to give you tips on managing it. Owning your flaws also makes you more relatable, and gives people more insight into you so that they can not press your buttons or help you once they’ve been pressed.