Zantac and baby formula

I have a 9 month old baby. At the age of 2 weeks he started having a lot of stomach problems which included constipation, colics, vomiting, blooding. After several medical examination it was found he had acid reflux and allergic to regular baby formula. He was placed a special formula called Nutramigen. At the age of 5 months we have noticed him to be very hyper, won't sleep much even during the night. During the day he might sleep twice a day (app. 9:30 a.m. and 4:00 p.m.) for maybe 45 minutes at the most. He wakes up twice a night when before he was sleeping for almost over 8 hours. Like I said this happened at 5 months old. He is on Zantac twice a day. Could this medication be affecting him in this manner. He at times looks quite tired, stays still for a little while and it seems like he recharges and gets more energy. This is also taking a toll on me as I don't get too much rest and the interrupted sleep at night is affecting me. Please let me know anything that you can on this situation or who or where you can refer me to for more research. I feel something is going on with this medication.