Does this sound like reflux or something else?

[Pinkstuffs]

My baby is 8 weeks old, he has always grunted and strained a lot which we put down to trapped wind. His digestion problems seem to be getting worse, in the last week or so he cries, arches his back, chokes and screams throughout his whole bottle (he is formula fed). He has now starting vomiting after feeds, it is quite forceful and it smells vomit-like, not the small spit ups he has always had. He cries for ages after a feed. He only poops every other day and he is very gassy.

We’ve switched his milk from SMA to Kendamil which doesn’t seem to have helped. The health visitor and GP haven’t been concerned as he is gaining weight but in the last few days he’s refusing bottles. He was born below the 2nd centile and is still very small for his age (but has been following his own curve). I’m worried he’s going to start losing weight.

Does this sound like reflux? Can I do anything for him myself? How can I get the doctor to take my concerns seriously?

I'm no expert, DD is 13 and healthy now, but it does take me back. She was born week 35 and weight went down to just over 3lbs and she struggled to eat a lot, getting into vicious cycles of over eating and throwing up, properly vomiting like you say. It was so worrying and unsettling for months seeing her so upset and I felt helpless but no issue was ever diagnosed and she did put on weight.
One thought I have reading your OP is could it be a food allergy?
Hopefully others will have more helpful things to say.
Wishing you all the best during this stressful time with your little one.