Back pain at twelve weeks?

I'm wondering if any of you early on ever have cramps.. Or if you're farther along if you did early on. Like bad back cramps that went down into your thighs.  Ive look up what round ligament pain is like and I have that too when I stand up quickly, sneeze, and such. This is different and I've had these once and I feel like I can't move. I get scared but last time the doctor said if it's not in the front it's fine and they went away after a few hours... Today seems to be more intense like the base of my back is about to bust through. I didn't have these before pregnancy except with periods. I'm just so scared somethings gonna go wrong but the doctor heard the heartbeat at ten weeks and said I was out of the danger zone. This is my first pregnancy. I used to have terrible periods where I would be cold and soaked in sweat because the pain was so bad. I couldn't even drive and the one time I did I crawled into my house and ripped out my tampon and cried on the bathroom floor until my husband got home.