Nexium dosing?

My baby boy is 4 1/2 mo old. He was diagnosed with reflux at 3wks old hasn’t been controlled since. Just went to GI and he switched him from prevacid solutabs 7.5mg once a day to nexium 10mg twice a day. I am giving it at 5:30am (1hr before bottle) and 5:30 pm (1hr. before bottle), he is in bed by 8pm and is still refluxing in the night. Not sleeping at all and seems to just get comfortable enough to sleep after am dose. We are only on day4 so I’m not sure if it just hasn’t built up enough to see full results or if I need to give it earlier in the evening. Any help or advice would be appreciated. I’m new to this board and desperate for first hand experience answers.