B.C.
I'd talk with your doctor about it soon as possible.
It could be muscular or joint related - relaxed joints can cause a lot of pain.
It could be a spine alignment problem.
It's probably nothing serious but pregnancy can put an awful strain on our bodies.
It's common for gall bladder problems to crop up.
When my Mom had a heart attack, she felt a pain in her shoulder and back of her neck (she wasn't pregnant) - women don't always feel pain from heart problems like men do (in chest or in left arm).
Tell your doctor all about it soon as you can and have it checked out.