Immature digestive system?

FTM. My little boy is 8 weeks (born at 37). He is formula fed on Hipp organic (started on aptamil but changed around 3 weeks). On both formulas, he has terrible issues with gas, and the HV put his symptoms down to that and ongoing colic. I've tried comfort milk, but he doesn't take it well at all. His awake periods are mainly spent what looks like straining and crying. He will do this during a feed too, so is never able to relax and enjoy his bottle. With gripe water, he's able to bring wind up okay after every 30ml approx. I recently started him on colief drops and since then he farts a lot! But again, he will strain, usually cry and seem in pain before passing wind and/or a poo. His poos seem normal, no mucus that I can see, and he goes every 1-2 days. I've read about infant dyschezia and initially thought it could be this but his symptoms are pretty much constant. Recently he has started bringing up some feeds, no pattern to it, sometimes a little, sometimes a lot, it can be during or after a bottle (seems to be since starting colief). Other times he has a feed with no issues and a very settled awake period, hence my confusion! Has anyone had a similar experience? Is it an immature digestive system? Excess gas? Dyschezia? Reflux? CMPA? I feel like he is never settled and spends his days straining to either pass wind or do a poo. Will this be something that will pass or is it worth chatting with G.P?