@37yr old mum I have had a frozen shoulder took a long time to heal . Usual frozen shoulder timeframe is 2 years to heal. I went to a physio who knew of a another doctor who gave injections of right into the shoulder blade. Very painful but very effective. On the bright side you may have an answer to treat your on going pain.
At the moment have rotar cuff shoulder injury which is getting better but again maybe six months before it is healed.
On the bc side have finished treatment cancer free at this moment. So far so good.
Lets hope your prognosis is good. I can understand it being a huge shock. best wishes.