Can I really get past this?

I have been answering others questions for almost an hour trying to work up the nerve to ask my own question...here I go...

I have been dating someone for about 10 wks. It has gone really well...until right after New Years when I get a facebook message from someone saying that she is his girlfriend. I asked her if they had been sleeping together (for the period of time I was dating him) she said YES. I confronted him and he denied it. He told me they did date for about a year, but broke up a couple weeks before he met me. He did admit to seeing her twice, and flirting with her a lot via text, but he did NOT sleep with her. I am not sure who is telling the truth. But I will say that we spent a great deal of time together the first 6 wks and he didn't have much opportunity to be with her. (Yes there is ALWAYS time to cheat) also I didn't find any inconsistencies or vague "going out with friends' things going on during that period.

He 'unfriended' her on facebook...I blocked her so she couldn't contact me anymore. But the things she said...have worked like a poison. I am having a rough time letting go of this. Even assuming he didn't sleep with her...the things she said...they have made it hard for me to get past this. Since that time we have spent nearly every night together and things have gotten quite serious. But I worry he is still texting her. I just haven't had the nerve to sneak a peak at his cell phone to check. I say to myself I am going to do it...then find some excuse not to... I am such a wimp.

I don't know if I can get past this honestly. I have never had to deal with invasive ex's or someone cheating. But I will say that this guy...he is awesome! I feel like I have met my best friend...and the sex....WOWZA!!!! So what exactly is my question....I am not even sure lol