Im 11 weeks as well. I would like to know the same because it feels terrible. I only feel it at night though on both sides.
I get it right around my tail bone and butt cheek on left side and sometimes it goes down my left leg. Mines sciatica I already had pre pregnancy and my belly weight is making it flare up more. You can get sciatica from pregnancy too. It's usually felt on the left but can be on the right.
I had that same problem I went to the doctors right away to make sure I didn't have a kidney infection or anything like that so I would go in and get checked because you could have some kind of infection
If its steady pain have your doc check for kidney infection, its fairly common during pregnancy. It usually leads to fever a couple days after the pain starts and can be fixed with antibiotics.
But if you don't wanna go get checked use a heating pad where it hurts and take Tylenol