Tightness in chest, 6 months later

Wondering if anyone else has the same experience as me and can offer any advice? I had a double mastectomy last October, with no reconstruction. I had 15 radiotherapy sessions in January. The whole way through, I’ve felt as if I am wearing a really really tight bra all the time (and I don’t wear one at all!) At first I thought it must be tight scar tissue, but after rads were finished, I’ve been having soft tissue massage from a physio and that has softened the skin and just below, but the tight feeling is unchanged. Now physio thinks it may be intercostal muscles that have taken a battering, made worse after radiotherapy. I don’t really think the radiotherapy made it tighter, although that did sound a likely cause. It was tight before then. Now I have chest expanding deep breaths to do - but those don’t seem to be helping much. I just can’t work out what’s causing it and what I can do to relieve it. It’s like my rib cage has shrunk, just across where my breasts were, and it’s v v tight. The op was 6 months ago now so I’m getting despondent about it - think I’ve given it a good long while to improve. If it’s any clue, it’s particularly bad at night, when I’ve been still for a while. It wakes me up if I try to roll over.

Would love to hear from anyone who could advise …