In a ltr 6 months now, both in our early 20s I decide to tell her about my previous experience (ex cheated with a chad). She casually mentions some male friend of hers(she told me previously that there was some 'tension' between them a couple of years before) who came home for the holidays from abroad and invited her out, she refused, but I could sense the guilt. She decided to tell this in the middle of my story, 5 weeks after it happened. Not sure how to react.

We agreed some time before we would have sex for the first time, but for various reasons it failed I did.. she hasn't done any advances since and always has an excuse, she's always very defensive and talks as if we aren't totally committed and anything could happen since then.

Edit: would like to add that we are not sexual equals, she's a virgin.

Would appreciate some advice, caramel666