Sciactic Nerve Pain (Pregnant)!!!

Ladies so i’ve been having some sharp pain on my left side buttock. When i walk suddenly i get this sharp pain i have to stop and press on it to sooth it a but. I could also just be standing and turn my body a bit and i get that sharp feeling. It hurts!!!!!!! I’m afraid to take a step because i suddenly get that pain. I’ll be able to walk with a bit of pain for a while then suddenly i will get that sharp pain. I’ve been thinking of going to the ER but idk does anyone have a remedy for this to go away? Also what causes it?!?

*17 weeks & 3days pregnant*