When I damaged my shoulder (I turned over a gokart) - there were things I couldn't do - like bring my elbows together at the front of me, or do reach behind to link my hands from above & below. It was all because of two little muscles that I had torn and it took a few weeks to get back to normal - even with all the physio exercises...

Have you ever damaged your bursa? If it was a side on impact that you took at rugby - it could be that - but the Ibuprofen should take care of it.

Are any of the muscles still tender to touch?

I also found the only way to sleep was Superman style, with a pillow under my armpit.

Wish I could offer some more support - but it could just be a case of time on this, as long as you do gentle stretching (crawling your hands up the wall etc...)