My girlfriend and I got together 5 months ago. We started out innocent, then one day bam! we were having sex behind a Walmart. We didn't do it much but maybe once a week we would make love again. Then she stopped being interested in making love. This was about 2 months into the relationship and I soon found out she was cheating on me...she had been with another guy and they did it constantly...after I found out, I told her it was over and she publicly cried for me back and after about a week I decided if she tried this hard for me we could work. Now at this point its been 2 1/2 months and for two weeks we went back to making love occasionally...now a month ago she told me she wants to wait until we get married to make love again...do you think she's really caring for me when she says that or is she...cheating again...?
Sex behind a Walmart, eh? ;)
Before you drive yourself crazy by assuming the worst, try talking to her about this. Communication is #1 in building trust. Convey your concerns, and attempt to understand where she's coming from. Why does she want to wait until marriage? What has led her to decide this for herself? Maybe she's having an internal battle between her sex-drive and her personal moral/cultural/religious standards. In other words, she may have had sex with you (and the other guy) before because her hormones beat her standards to the punch. Perhaps now she's feeling more self-restraint, and wants to go back to respecting her original beliefs.
Also, keep in mind that just because she had sex with you before does not mean she wants to (or has to) have sex with you again. It's her body, and her choice. If she want's to stop having sex until marriage, you have 2 options: respect her decision, or rethink the relationship.
In terms of the cheating factor, again, communication is key. As is often the case for most people, once the trust is broken, it can be extremely challenging to rebuild. And while you may never be 100% sure whether or not she's cheating, communication will increase your chances of knowing the truth, and in turn, possibly strengthen your relationship.