My immune system sucks

(Well, apart from the obvious fact that it destroyed my pancreas)

One day of a music festival and again, I've been having a cold for the past few days. Every time I try to get healthier by working out more, I catch something, fall off the track and have to start over again.

Anyone have an idea how to remedy this? I'm type 1, have been for about 5 years. Eat keto/paleo, numbers are under as perfect control as I've ever seen them (A1c of 6,5 with about 1 hypo per month)...

Kinda done with it really.