Hi,
I've had cramps on and off since becoming pregnant usually about once or twice a week but a few days ago I had them so bad I felt the same as if period was going to arrive and they continued for 2 days! I rang maternity assessment unit and they said as long as there is no bleeding or waters breaking that it was most likely ligaments stetching. Funnily enough my stomach has grown since then so I am putting it down to growing and cramps have stopped.
I was really worried though and considering going to hospital to get checked over etc.
I'm sure it will be the same for you as in growing pains, as long as you don't have bleeding.
x