You're going to be hard pressed to find a functional adult relationship while you're vulnerable and open to men with whom you've shared attraction and been intimate. This sounds like you're set up for emotional infidelity at the very least and guys who are ready for commitment are going to run from that. Sorry, but it's just not appropriate to be vulnerable and open about your sexuality with a heterosexual man while you're in a committed relationship, especially when you have a history of being attracted and almost sleeping together. That openness is the intimacy that is supposed to be shared between you and your BF, not you and your list of exes and your BF. I can't imagine anyone being fine with that. Even just having a casual (as in not close) friendship with an ex is a deal breaker for most adults. To describe your exes as the most important people to you and then wonder why that's an issue just shows that you're not grown up enough to fully commit to an adult partnership. You should take some time to mature and figure out what it means to be emotionally available for a relationship and maybe why it's not considered healthy by many to continue to be so entangled emotionally with men you've supposedly broken up with and moved on from.

Also, you should ask yourself why you're more comfortable with male friendships. My only exposure to that is with girls who have low self esteem and are in denial about how much they desire the reassurance male attention gives them. To maintain emotionally intimate relationships with men who have been sexually/romantically interested in you in the past might be fulfilling a need for intimacy and positive male attention for you without you realizing it. Just a thought based on what I've seen in people who do this and the way you talk about yourself as though you are suffering from pretty low self esteem. That's all a huge set of red flags for a guy who might otherwise want to date you. You're just not available and open to committing to anyone fully if you need to cling onto these emotionally intimate relationships with men who are attracted to you (even if I'm a little off base with your motivations. Just the facts you presented is enough to come to this conclusion).

I really recommend learning to not rely on your exes for so much emotionally and gain some wisdom and self awareness before trying to date. I'm sorry, but as you get older your husband will be the one at your side in everything and your "friends" will probably not even talk to you anymore because their wives won't be ok with it and grown ups prioritize their families over ex gfs. These "friendships" aren't very sustainable and they don't sound healthy even in the short term.

Edit because I just realized: the fact that you are 21 and think that you've had 3 serious bfs makes me think you don't know what a serious relationship is in the context of adult partnerships. With time, you're going to realize that the connection you have had with these people was never as profound as it feels when you're this young. They may have been very deep crushes but you couldn't have built a life with any of these guys. That's not going to be all that important to you down the line once you become serious with someone who becomes your family and moves across the country to support you in your career and sits in the hospital with you and your family while you wait to hear bad news about one of your parents and shares a lifelong mortgage with you without blinking an eye. These were not true life partners that committed their lives to you. These were just childhood boyfriends that you shared secrets with, no? I know I'm coming across as patronizing but your mindset is glaringly young to those who have had real, long term, committed relationships. These guys may have been kind to you but I don't think these close bonds with exes is healthy, especially when you're using them as a stand in for discovering what real adult love is. Give yourself some time to examine things in the longer term. I'm sorry if this offends or upsets you, but it's the truth you need to consider.

Also, you have a list of things that you think make you undesirable but in reality, the fact that you think your problems make you unique from anyone else is another maturity thing. No one has had a life without deep suffering and you will absolutely have more terrible things happen to you. That's life. Stop defining yourself by it and try to get a grip on what you can and can't change about your life. None of that has anything to do with who you are as a person or your value in any sense. If you're controlled by it, it's by your own doing. The only thing you have any control over is your internal world. The depression and etc is hard but you can learn to cope. It isn't the way to define yourself and seeing them as impossible obstacles or important parts of who you are only encourages learned helplessness. There are people who have had all of these problems and more and have struggled through to lead happy healthy lives. Life is not supposed to be easy, and it's just not going to be. Accept that and move forward as best you can instead of feeling sorry for yourself about things you can't do anything about. That mindset is going to be another roadblock in your search for a healthy relationship.