Sciatic pain??

So I am in the middle of 20 weeks and just started working at 17 weeks. I’m on my feet a good 7-8 hours 5 days a week so the soles of my feet start to kill me (I bought insoles not quite working). Anyways every night when I begin to relax I get this stinging pain in my left butt cheek that goes a little up to the bottom of my back only when I try to put pressure on my left leg (meaning I’m limping around). Almost like my legs given out on me so I was just wondering if any of you are familiar with this and if it might be sciatic pain. Anything would help! Thank you!