Why do you think all these things have finished. There will be nothing to stop you from socializing. When you say you see other people doing things, normal things, how do you know they haven't got a form of cancer. Statistically some of them will have and others will know someone who has.
My friend was open about her cancer (she had breast cancer and had a mastectomy) and although she felt shit during the treatment (chemo) we used to do all sorts of things together. From the mundane like shopping (she didn't want to drive for a while when she felt rough) to going to plays and concerts and the best was a 2 week holiday in Barbados. She would go to F1 grand prix in England and in Monte Carlo.
While you won't be able to do everything you used to do, there will be other things instead. Take all the little wins.
A couple of years ago I should have died from a combination of various problems: sepsis, pneumonia, the beginning of liver and kidney failure, TIAs and a massive internal haemorrhage. I had blood clots in both legs and the plastic surgeons took one look and said the right one is coming off and the left probably. They are still attached - win, the sepsis and pneumonia seen off with anti-biotics - win, haemorrhage had blood transfusion, they did CT scan but couldn't find the cause and it didn't recur - win, TIAs under control - win.
In addition to all this I was flat on my back, I couldn't sit up, never mind stand and walk and my goal was to be able to walk, on my own, to the toilet (because of total lack of mobility I was in continence pads). The day I did get to the toilet was a MASSIVE WIN. It was literally in the same room 6 feet from the bed (I was in a care home by now) but you would have thought I had just won the London Marathon. It took months and months of physio to learn to walk again. At least you won't have that problem. The various specialists I saw over my 3 months in hospital said it was a miracle I was still alive but I was determined to live, if for no other reason than to be as big a bloody nuisance to as many people as possible for years to come.
From what you say you are much younger than me and with lots to live for, not least to see your child grow up and have a family and become a granny - that's a goal to aim for and more fun that going to the toilet.
Don't give up, let your family and friends know because they will want to help you and support you. The more people you tell the easier it will become. The idea that people with be nudging each other and looking at you is all in your head. The last thing I would think when seeing a total stranger in the supermarket is "I wonder if they have cancer". I might think, "I wonder where they bought that jacket, top or pair of shoes" The more you let it take over your life to the exclusion of everything else the worse your mental health will get. This in turn will make everything worse than it needs to be.
Learn to lean on the people who love you and don't shut them out because they will want to help you. You say you don't want your husband to tell anyone, but he will need support so that he can support you.