Are your sets put in by hand or with an inserted.
I'm an old type 1 with a pump and slim and muscly. I too find sets can be painful to put in on occasions..But putting them in by hand I find that if they feel painful on way in.. It means I'm not in a good place.. So I try another place.. Sometimes just a couple mm's away from the one that was painful.
I cant use my stomach at all because of sets always being painful there. I only use my bum or legs...
I was petrified too with putting in sets 1st because I got so much trouble with stomach which I was told was the best place to put them.
I find my bum better than tum!!
Persevere, its worth it...