for our 7 month anniversary my girlfriend gave up her virginity, it was something we were both looking forward to, and something we both seemed to enjoy...but in the past week she's been acting really weird, and becoming more distant. She always has something else to do or somewhere to go rather than be around me, and I don't know how to ask her about what's wrong without leading to a break up, let alone what to do to try and save our relationship if I can't avoid the break-up conversation.
Perhaps the experience was not what she thought it would be and she's reacting. How long ago was this? Months ago or a matter of days? Did you and her communicate your views on what sex means to each of you beforehand? Either way you'll need to communicate and just ask her. She could be withholding some important information or it could be something silly she's embarrased about. You'll never know if you don't ask.
Losing a virginity for a woman is a HUGE deal. Not something that should be taken lightly and it sounds to me that you care very much for your girl... so I am glad to see that you are not running for the hills.
That being said, she is scared and really she lost a major part of herself that night. She lost her innocence - which adds a lot of pressure and emotional ambiguity to her current situation and thoughts. What she needs is for you not to pressure her again until she is ready... but to be there and support her. She needs to know that it was a gift - something that you cherish and that you respect her for the person she is not just the sex.
If you're unable to have an open communication line with someone, you probably shouldn't have had sex with that person.
This all could be subconsciously you're perceiving to be a larger problem than it is currently. If she really is busy this week, take it at face value. Ask her if anything is bothering her, let her know that you want to see her, you want to take her out etc;
This certainly isn't something that should be leading up to a breakup and this is all new territory to her so now she's out of her comfort zone. If you were previously a virgin as well, its new for you as well. If you were not, you should understand that there are probably a lot of questions going through her mind right now depending on the experience etc; Comfort her, reinforce the decision that she made to have sex with you and allow her a little space to really digest what happened.