What should I do?

I'm currently 15 weeks and ever since Monday night (4 days ago) I've been experiencing pretty intense cramping and starting yesterday my lower back is having like spasms. I've previously had a miscarriage and I'm really scared that's what this is even though I'm having no bleeding. I know I could be over reacting and Im just really worried. I called my OB and they haven't called back and it's been a while now. I asked my mom if I could go to emergency care or the hospital and she said I was being ridiculous but the last two days I haven't felt the small movements of my baby that I have been feeling. I'm just really scared and my mom says I'm over reacting and doesn't want me going to the hospital. I just don't know what to do.

UPDATE: I stayed the night at the ER, my urine and blood looked fine and my baby girl looked perfect on the ultrasound. They diagnosed me with a threatened miscarriage and recommended I see my OB as soon as I could. Thank you all for replies.