Sudden extreme back pain?? Help

I'm almost 37 weeks and sitting in the car when all of a sudden I got excruciating back pain like literally felt like someone was constricting my lower back and it hurt so bad I could barely breathe through it. It was mostly intense pressure in my back and hips.i had to pee REALLY BAD and usually that happens when I have to pee so I went pee and it went away a little but I still feel the pressure and I went poop a little (tmi) but it I still feel the pain in my back however it's constant so I don't think it's contractions. It also hurt to try and poop and not much came out and I still feel the back pain. but like I said its not like it's coming in intervals. but it just came on so suddenly.  Ugh. Idk what's going on 😭