I went to the dr. today and got a positive uring test for pregnancy! But I have a few ??'s.?

Yes. Cramping is usually a sign that your uterus is preparing to grow. As for back pain, it'll be there off and on the whole way. You may get ligament pains in a few weeks too. It feels like a sharp shooting feeling in a diagonal line on your left, right or both sides, down to your vaginal area. This is all normal, even with a little spotting for a day or two (very light and doesn't continue all day, just off and on). Congratulations!!!