Me and my girlfriend...?

Hello, I would like to have some help about my relationship... I meet this girl 9 month ago, at the very begining, for me it was only about losing my virginity but once that happened, I started to love this girl. I am 19 years old, she is 20. We always had a good time together she is also my bestfriend. The main issue is that I am a very jealous guy. One of my friends used to have her as a fuckfriend and when he is drunk,he can't keep his mouth shut so I've learn thing about her that I shoud'nt have known ( mainly about her sex activities in her past). Yesterday, he asked my girl if this guy that a hate named carl had a big dick. he thought that I already knew that she used to sleep with carl 2 years ago but I didn't. I feel like **** right now. I'm telling myself that if she could do that with him, anyone would fit her. I love this girl and I know that she would never cheat on me, she has always been there for me but I just can't see myseft telling her that I love her while making love to her. I don't think that I will ever be able to get out of my head the image of this asshole being on top of her in the past. I would like you guys to help me about this I am lost at the moment and it don't feel good at all :(