Baby screams to poop

Okay so my son has silent acid relux on meds which can cause some constipation. He is 8 weeks old.I have tried everything today : bath,bicycle legs,massage.rocking and bouncing. He finally pooed a tiny bit but it has become a battle. He screams and screams trying to poop but it doesn't come out in pebbles or anything.

Would a change to gentler formula help?? Maybe. His ped appointment is this friday.

He has always struggled with gas since I stopped breastfeeding and we have him on similac sensitive and i honestly think it is making his gas pains worse.

I was thinking of switching to nutramagen formula because from what I have researched alot of babies that have reflux seems to be due to an allergy.

Until he poops first thing in the morning...its bad...hes screaming, grunting and it breaks my heart cause he is 80 percent of the time a happy baby until he has to poop.

I should add i tried to give him his usual bottles of similac sensitive today. He refused to eat it st all. Just made a bottle of nutramigen and he gulped it down...