Desperate now, any advice?

[ShakeVigorously]

I have a 5 week old baby, born at 34 weeks.
Everything started fine, home after a week in Scbu.

A few days after he came home the feeding issues started.
Struggling to take a feed in less than a couple of hours, holding his breath while feeding and going blue, shocking wind (then trapped wind after), vomiting.

He makes the most awful noises constantly. His poos are soft but strains all the time with high pitched moaning or roaring!

I changed his milk because my dd had a milk allergy- no difference. He's back on aptamil now on advice of gp who thinks it's reflux.

He's had gaviscon- no difference.

He's on ranitidine now- first 2 days fine, now back to square one.

I literally cannot put him down!!
I've tried the usual propping up the Moses basket, massage, holding him upright.
Nothing helps. When he does sleep it's little naps.
Spoken to gp and HV, not at all concerned because he's putting on weight and having wet and dirty nappies.

I literally cannot cope anymore 😢

I'm really sorry you're going through this and can understand how horrible it is. My DS was fairly similar to yours and used to scream when we were trying to give him a bottle. We have tried everything including spending a small fortune on bottles! In the end dr Browns bottles with dentinox or gripe water along with colief did the trick. He's not 12 weeks and although is still sick sometimes he is no longer in pain. Unfortunately a lot of it is probably due to age and how their digestive system in developing. If you are really concerned I would push to see the GP again.
Hang in their OP, it will get better I promise.