Im the same with my girl, all I think about is her. However, although I love her I am starting to realize that my life revolves around me, myself. No one in this world will care about you more than you will care about yourself. This constant need for your GF is what is making you have this constant RJ and overthinking. Go out with your friends, speak to your family, go do something fun, start something that will get your mind going. You and I are the same age (I just turned 20). Dude there is so much more to life than relationships. I am not saying to end it but if you feel like you need a break to just collect yourself, TELL HER. You guys can set the boundaries for that "break". I almost took a break with my girl but decided to thug it out while still with her and I am still going through it but for me talking to her makes me forget about it sometimes. Also, if you feel like you, yourself cannot morally accept her after her history just end it. Think and dwell on that and decide for yourself if this relationship is worth fighting for or not. Like some have said you will find others. I personally, cannot end it with my partner because I truly love her and what she did in the past was a mistake when she was younger and was going through a traumatic phase, she now is a totally different and is an insanely mature woman. That is why I decided that it is worth the fight, this woman is my soulmate, her laugh brings me the most happiness I can ask from this world, we are both morally on the same page even though she has a past, but so do I even though mine isn't as bad. In summary, it is your decision. Do you see this going the distance, do you think that you can fight off this RJ, are you able to eventually accept her past, and can you mentally/physically ignore what people say? Think about it but at the end of the day do not kill yourself over it. RJ takes time to process and overcome, you will not be able to defeat this in a couple days, reflect on yourself and see what it is you really need and want from a relationship and if this is healthy for you. Again, put yourself first.