I used to work in the sheltered housing sector and I know how very difficult it can be to make the decision to move into it. An important thing to remember is that you are still independent, you can come and go as you please - a lot of our applicants weren't aware of that and thought of it more in terms of what you would expect in a 'care home'.
When I was there, 'Stay Put' was introduced, which meant that more services were provided as and when needed, so that you didn't need to go through the upheaval of moving again if there were further health issues.
I left that employment years ago, so am not sure what the current schemes have to offer, but things have improved no end in terms of assisting people to retain their independence as long as possible.
We have an Aunt in the NE, who rents a bungalow, council owned, in a supported scheme for residents over the age of 55, but uses Care Call for emergencies. CC are marvellous and react immediately if there's a problem.
Have you had a look round any schemes in your area? It might reassure you if you see what's on offer, especially as they probably all vary.
I can honestly say that, when I was working, I don't remember anyone who regretted moving into sheltered - once they'd come to terms with the fact that the time had come for it to be the best option for them. As with any move, it does take a while to adjust and sometimes going into sheltered takes a little longer than a 'normal' move.
As Glamma has already said, have a word with your housing association, I'm sure they'd point you in the right direction.
Good luck