Has anyone been feeling this pain too?

Isabel
I'm currently 15 weeks 1 day. I've been getting shooting pain in my lower back towards the top of my butt. It usually happens more when I work a lot and have been doing a lot. 
It'll hurt so bad that if I'm walking I won't be able to put weight on that leg, or if laying down and then I try to get up it hurts so much. 
I heard it could be Sciatica, but I also don't know if it's too early to get that, 
And if anyone had got it previously or now, any advice??
This is my first pregnancy and I heard it only gets worse :(