Help!!! Very unhappy baby and don't know what to do.

I'm a ftm and my baby was premature. He is 3 month old (1 month corrected age). He suffers from acid reflux and has been on ranitidine for 2 weeks now. My problem is since about 4 weeks now he is never content. He's unhappy before a feed,  screams during a feed, really unsettled after a feed. This started around after his 1st vaccinations. He use to be able to do tummy time but now he jist screams.  It's getting me very down and I really just want to enjoy having my baby but feel very useless as i can't keep him happy. Something I've tried usifn are infacol and colief.  Didnt rrally work. I use carobel in his milk ( i use ebm and c and g first infant milk.  Any suggestions please, I would really appreciate.