Cramping

I have been having a lot of cramps. I went to the doctor yesterday since Ive had a little spotting the last few days, and they did an ultrasound. He said everything looked great, and he didn't find a reason for the spotting. Has anyone had this? The cramps hurt, and I have gas pains too. It's hard to tell the pains apart sometimes... They saw a heart beat on the ultrasound (131 bpm), and I am measuring at 6 weeks today.