My surgeon warned me to ignore all the funny feelings I would have at first - but as I got a persistent seroma (fluid) on the site, it was hard to tell what was causing what. No pain, but tightness certainly and occasional aching caused by fluid. The worst was the sloshing noise when I bent over - that was definitely the fluid! Once that problem was resolved, I have had very little problem. There is a degree of numbness, also in my armpit - not as bad as the first few months but four and a half years on, I suspect it's there for life. It's not a problem - I used to have difficulty feeling where to put deodorant, but I can fee that now. Can't really tell hot or cold though - luckily I don't wax my underarms! Occasional tightness you may still get - it's the scar tissue and is particularly noticeable if I have been exercising strenuously, or doing something I don't normally do. Just tight though, no pain. I too am happy with a prosthesis, and haven't had any issues with it and my mastectomy site. I have had a lot of massage (for the seroma) and I reckon this helps everything so may be worth a shot. Best to get a therapist who works with cancer patients such as a lymphoedema therapist, who knows what they are dong. Good luck.
