Pain in the ass

I am blaming my ass pain being pregnant. I do not know what else to do.
I've got this muscle, or something, on my right cheek that is just like, howling in pain. It has been bothering me for weeks.
"You need to have it looked at", Rex says. "Ha!" says I, " I am indestructible, invincible, unconquerable, unquenchable!" He looks at me and sighs, but I am also stubborn and pig headed.
The running theory was that it was somehow related to my s-i joint, which has been wacky for a while now, and since the muscle in question is in close proximity to said joint we (my trainer and I) figured that it was related. And honestly (thinks me), a sore ass cheek, so what. It only hurt (past-tense) when I was in-between sitting and laying, or when I was rolling over so basically only at bed time.
Last week maybe it started hurting when I was doing lunges. My body is started to appear more pregnant (my belly is starting to pop!) and as such my center of balance is all wack-a-doodle and I have to work on keeping all my damn muscles engaged when I'm lunging.
Well apparently I have to keep my muscles engaged while I'm walking through a parking lot too because this morning I woke up with a sore ass cheek and the situation has not altered in the slightest.
"It's right here" I say to Rex, pushing on the offensive spot in line at our local chain coffee shop. He looks at the ceiling, out the door, away from me and nods. I guess that pushing your ass around in public is embarrassing or something.
Can I just say I am totally okay with embarrassing my husband wherever we go, but the idea of writing to my doctor and telling her that my ass is killing me is nearly completely out of the question. And I mean, really, what is she going to do? Nod and tell me that my body is undergoing a lot of changes right now and blah blah de blah. Put some ice on it.
So no, I am not going to write to my doctor, because complaining about a sore ass cheek that might possibly be related to a wonky s-i joint seems altogether too vague for corporate medicine.
I am going to suffer stoically. Except for when I'm in public with Rex, then I'll have to remember to complain loudly, with full visuals, and often.