<human>: Can you condense the text into three sentences or less?

So I have just started dating this amazing girl. It has been about 2-3 months now and things are going better than any relationship I've ever been in but lately I have been having this nagging anxiety when thinking about her and her ex-boyfriend. 

Her and her boyfriend previously dated for 3 to 4 years and she has told me that for a time they were very happy together but that he broke up with her, citing religion as the reason for the dissolution of their relationship. 

My anxiety has stemmed from the fact that she has told me how happy they once were and that I know the relationship was not ended on her own accord since she was broken up with. Additionally, she has recently told me how much better she feels in this relationship as opposed to her past one with her ex. While this sounds consoling, I have felt like she is only measuring my worth next to the worth of her Ex, and not simply based on where she feels this relationship stands on its own. Apparently there has been little to no contact between them since their breakup more than 9 months ago, and I am inclined to believe her. 

I know I must sound super paranoid but I really do like this girl and just wish I knew how to navigate through this muddy water without such anxiety and stress. What do you guys think about this? Should I be concerned? She claims to be really happy and falling for me but the details of her breakup make me feel like their might be residual feelings. How do you experts think I should handle this situation? Thanks and good luck everyone :)
<bot>: My girlfriend and I have been dating for a short time, her past longterm relationship has me feeling anxious. What do I do?