I do know one person who has to change the canula every day, not the tubing, just the canula.
I would change the type of set. What do you use at the moment? What pump are you on?
I could well be the way you are doing it, who knows, it could be a number of things. Have you spoken to your DSN about it.
Please be careful. If you think in any way that any of these lumps could be an infection get antibiotics immediately, don't muck around. These site infections are really nasty and are very deep.
🙂