My Girlfriends previous Ex's...?

Hello. Thank you all for reading, and I'm open for any and all advice. My girlfriend is 21, and I am 20. She works full time and I am a medical student, life is good to say the least. We have been dating now for 7 months, and the other night parked outside a McDonald's of all places eating ice cream, we started talking about previous relationships. I was her first. No one had with her before me, but she did have a relationship with a guy for 2 weeks that led to a couple blow jobs, and also she had a "hook up" with a guy she met online 1 week before she met me where they went to a parking lot and she blew him. She told me that she swallowed both of them. Followed with "the guy I dated for that 2 weeks had a huge ". Don't get me wrong I don't think in all my reason that she said any of this to be malicious, I simply think it came out. But now, its been 5 days and I still can't get over this. Every single day I think about these guys shooting into her mouth.... the same mouth I kiss, and it makes my blood boil... This isn't healthy and I have to get over this ASAP or its going to ruin our relationship. I have talked to her about it and she apologizes relentlessly, blaming it on her low self esteem back then, which makes me feel worse because she needed someone to protect her back then, not take advantage of her in a parking lot... Its just becoming too much to handle, and I think about it many times every single day. Its affecting our love life, and my schooling. I know its something that she should have never shared, but its done now, and I need logical advice as to my next step. Please and thank you.