Why do I keep having bad reoccurring dreams about my relalationship?

I think you're having this dream because you've obviously been affected by what your gf did and you haven't gotten over it yet. The fact she sent pictures to your best mate is pretty wierd even if she wasn't with you at the time. Either she was angry with you and wanted to apy you back, or she was messed up on drugs/alcohol and didn't know what she was doing, or she's just not very nice. I guess you haven't been that good either. Anyway, you either have to put it ehind you and stop checking up on her all the time, or you have to move on and call it a day. And hopefully you both learn from you mistakes and treat the next person a bit better.