So I'm hoping to add a different perspective to all of this, that may be closer to your partner's view/position. Back when I was not with my long-term boyfriend, I was a bit more loose as well (I was more unhappy and and the two were connected).

I offered to have threesomes with my friends during this "loose time", because I honestly didn't care who was there. I was in it for the fun of it.

My current boyfriend and I have talked about participating in a threesome, but each time, we opted out. Mostly because I care so much about him, I don't want to share him. I don't want anyone else to have him in the intimate way that I have the honor of having him. I don't want anyone to have that experience with him.

I understand that we both have different sexual histories and we have left those in the past, but for who we are for now, I don't want to share that with anyone else.

From the post, OP, it sounds like you are focusing on your insecurities and are using her past as a way to continue focusing on them. You said you had insecurities before learning about her past and then they became overwhelming when you learned about her past, but the common denominator has been your insecurities.

I definitely think you might need to take some time to look at yourself and continue to work on yourself, not just physically but emotionally and mentally as well. I would also try to stay away from drugs/alcohol/gambling/sex as a means for coping (cross addiction is a nasty thing).

Also, I know you asked for advice, and I really hope this all helps, but please try to take the advice to heart. I see a lot of excuses and trying to fight the advice of others. You came to us, and it might be a scenario where you were looking for someone to agree that she needs to give you exactly what you want, but I'm not sure you're going to honestly get that response here (maybe you will, it might a troll. I have no clue).

I really hope this works out for you OP. You are still quite young and I'm afraid your immaturity in the situation may cost you a relationship with a very understanding and forgiving individual. Good luck to you with this, sex in a relationship is difficult for everyone involved.

Please try to be as understanding and forgiving about her past, as she has been for yours.