I just completed my first solo trip where I couldn't carry anything. (I was supposed to travel with my husband but he had to cancel)

I had a 6 kilo roller with me for the 4 days I was away. But I couldn't lift it up stairs or into the plane, nevermind into the overhead bin.

I could have asked for wheelchair assistance, but I declined. This probably put me in the same situation as you.

I asked for help from other passengers.

With Easyjet, I explained my situation to the gate staff. They offered me priority boarding but didn't have staff who could help me with the stairs. The solution I presented was accepted, which was that I could ask a passenger to assist me and they would be allowed to pre-board along with me (it was easier to ask with this incentive). The person I approached was very nice and offered to help me disembark. Turned out not to be necessary as the couple I sat next to helped me instead.

For the return trip on Ryanair, a nice strong man who I spoke to in the airport helped me on and off with my bag (we were the last to board).
I came back via a different route (London Luton - I'd cut short my original trip and booked an earlier return last minute) and ended up unexpectedly facing stairs in the actual airport. A ground steward helped with one flight and radioed to a colleague who was there to help me with the second flight.

I'm sure I looked young and fit when I asked too. Saying you're recovering from a dislocated shoulder explains your situation immediately.

I can sit, and I can walk, what I'm not very good at is standing around. This is why I really didn't want to check in my bag. This was complicated to explain, but I never needed to.

If you are uncomfortable about asking for help lifting your bag into the overhead bin, I'm sure the cabin crew will assist you.