I'm very sorry, this is gonna be a long post but I really have to vent about this

I'm an almost 20 year old guy now with an absolutely stunning girlfriend (who I do not deserve at all), studying medicine with an allround good financial situation. I have a small studio my parents pay for, I'm able to afford anything that could possibly make me happy and I go to the gym 5 days a week, so I'm in pretty good shape.

Why am I telling you all of this? Not to brag, no, I hate to admit that I have every single one of those. Why? Because even though people tell me I have all those things and no reason to worry, I am insecure as hell.

I struggle with pretty much every part of my life, with the main thing being my relationship. My insides just cramp together every time my gf mentions another guy or just even mentions a context with guys involved. Every interaction she tells me about from guys asking for her number at parties to simply her neighbor who threw out the trash yesterday just makes me want to crawl into some dark corner somewhere to never be found again. She knows about the insecurities that I have, but I have never truly explained to her the vast impact it has on me, because I try to hide it as well as possible. I'm not someone to prohibit her from seeing other guys or talking to them, because that's just not fair on her. I just let her be, don't comment on it and take on the pain until it goes away...

But that's not all, I've got it as well when she's out with her girl friends. When she mentions that she's going out with them I just enter this black hole of overthinking. I know they talk about relationships, I have a strong feeling that her friends don't really like me and I always have the feeling that all my toxic traits or bad sides will be exposed to them, even though that's not something my gf does. I can't explain why I've got it, because I know it's not rational. It's just there...

Moving on from my relationship, I'm pretty much insecure about every single other thing in my life. I struggle making friends and I am afraid people pity me for it. Even though people tell me I'm looking good in an outfit or complement my posture so now and then I still don't see what they see, I just see this lanky, skinny dude with some ugly belly fat and a deformed face in the mirror. I love to go to parties, but have a hard time to find people to go with, which makes me scared that I'm just a boring person to go out with (the few nights out partying with my gf have also all been pretty bad). When I try to talk to people they often seem nice, but never do I feel like anyone actually has any desire to talk to me or even be in my company, which makes me scared that I'm just an allround shitty person.

I could go on and on about the insecurities I have, but I think you've got a pretty good picture right now about how these insecurities behave like stage 4 cancer: they are all over the place, and even though sometimes I might feel like they're not there, sooner or later they'll just start growing again and I'm back in the mud again. Living like this is an actual hell and I've tried therapy twice already, not once has it worked out. The therapists always made me feel like I'm just seeking attention and that nothing's wrong with me

If you've made it all the way to the end, thank you for hearing my story. I really needed some time to vent and this seemed the ideal opportunity.

TLDR: I've got crippling insecurities in all aspects of my life, mainly my relationship, and feel weak and unworthy because of it.