I had this pain too during both my pregnancies. It was AWFUL pain. It was worse than labor. I went to my doctor about it twice and she said it was probably the muscle stretching and there's nothing I can do about it. It got worse the larger I got and I tried everything to ease the pain. Finally, I put Icy Hot on it and rubbed and rubbed and rubbed. I also bought a wrap for athletic injuries and wrapped it under my breasts and wore a cami under my clothing. That helped me stand upright and act fairly normal when the pain was moderate. When I pressed against my ribs and kind of held myself together it helped, but who can do that all day?! This was so frustrating. No one could help, people thought I was a wimp, and it was constant. After I delivered my over 10lbs baby and I knew I had something to compare the pain to, I knew I wasn't any wimp. Right after my child was born the rib pain became dull and tingled like how an asleep foot feels. After a few days I had hardly any sensation at all in that area. With pregnancy number two (my kids are only 13 months apart) the pain was exactly the same but now it was on the right side. Same everything and it was miserable. Now my babies are one and two and I still don't have a normal feeling in my ribs. I have only heard of one other woman complaining about this. No one seems to no what I'm talking about.
Just try to push back on it with wraps, etc.
Please let me know if you discover anything out about this. I want to have more children, but I don't want to go through this again.
Good luck!
E.