hi girlygirl,
I had similar pains after having sex but this was midway through my pregnancy and i was told it was cervical errosion.
Your GP may decide to send you for blood tests and an early scan as period pain can also be a sign of something else.
I have also heard women claim to have implanation bleeds and pains on or around when thier first period is due.
So all in all it could really be anything, maybe even stretching pains or the womb contracting normally, so try not to worry until youve seen GP
Good luck at the doctors!