Girlfriend is moody after sex

Ok so me and my girlfriend have started having sex just recently. It has been protected. After sex she gets moody for a couple days...but this time she has been very moody....It is worrying her that she is this agitated and irritated all the time. Could it be that we have just gotten on Summer break and she is constantly studying for her sat exam that the stress is causing her to feel this way? or is it possible that she may be pregnant....that is our biggest concern...we had sex a week after she finished her period....i would really appreciate some serious advice on this. Thank you.

[sandy828]

if shes always moody then i doubt shes pregnant.
moods change all the time especially if shes a teenager.
i wouldnt worry about it