I need advice

My son was diagnosed with reflux at 1 month. My husband and I were surprised, he had always been fussy and spit up but we didn’t really correlate the two. He was breastfed at the time , but we were supplementing with Similac. We gave him the prescribed Zantac for 3 days and he seemed even fussier so we stopped using the Zantac. I continued to breastfeed him but stopped using the formula. He continued to spit up, but it got better and he was becoming less and less fussy. Then at 3 months we weaned him to formula. Ever since then we have had problems. The Similac was constipating him which caused him to spit up more. He seemed really uncomfortable. I tried nutrimagen for 2 days. He was even fussier and had a huge runny bowel movement. That day I took him to the doctor. She said to go back to the Similac and use doctor Brown’s Bottles. She said that since it seemed like the constipation was making the reflux worse (which I agree with) to give him pear juice when he didn’t have a bowel movement for 24 hours. We also started the Zantac again. I followed this for a couple of days, but then decided to try Nestle Good Start b/c I had heard good things about it. We are on the second day and he is spitting up constantly. Much more than on the Similac and he is not even constipated b/c he had a huge bowel movement yesterday. My question is should I keep trying with the Good Start? Is he just adjusting to it or is there some reason why the Good Start could be causing him to spit up more? If anyone has any thoughts I could really use some help.