Well, if it hurts that badly, then do get it checked out! You've had a rough road and you are right to be careful.
I've had a chronic rib ache on my right near the spine. It flairs when I sleep on my side for a while, then turn over. But I think it's pretty normal, even though it really hurts - it goes away quickly enough when I move, and things "settle."
I get a similar one near the bottom of my sternum during sleep (on my side again), or if I slump while sitting, and the whole sternum still hurts a little if I try to use my arms to get up from a chair or the bed. I'm at 10 weeks today, and the top of my incision is still bruised and swollen, too. Plus my left shoulder still screams at me. It's all related to surgical "abuse."
So SOME aches and pains are normal at this stage. But yours may be a sign of something more significant. I can't imagine a bra band bruising you that badly. Mine irritates my scar sometimes, but nothing worse.
Why don't you go to the doctor today if you can?