Pelvic pain & pain in my knee

I’m 18 weeks & 1 day pregnant , I’ve been having the absolute worst pelvic pain . It hurts to walk , turn in bed , just move in general . I can’t even wipe myself when I go to the toilet cause it hurts to touch . But today as I was getting out of the car ( my 1 year old needed pull ups ) I caught the sharpest pain in my knee & I had to grab onto the car to stop my fall . It became bearable then stopped , im laying in bed now & went to turn over & the pain is much worse . Please can somebody tell me what could be causing these pains , this is baby #4 . This is the first pregnancy I’ve had these pains so early on ! Please Tylenol doesn’t help & idk what else to do . I’m finna go soak again & pray it helps , but if not can somebody please help with some way to relieve the pain .

Side note : haven’t had sex in over a week , so I doubt it’s due to that !