I have felt the same way in both of these situations.

1) She really seemed distant and VERY reluctant to talk to me about something she told me that she wanted me to forget about. I hope she didn't cheat on me!!

2) This is the hardest thing to try and ignore and hope will get better in time, because if something BIG did happen and she is feeling guilty about something, then she should come out right and tell me instead of hiding it and playing it off and hoping I'll forget about it. Because I can't forget about it!! It's weighing on my mind way too much now.