Switching to Formula..

Hello ladies, I been nursing my son for 5 months now. Even though he is gaining weight and everything seems to be on target, the older he gets the harder it’s getting. I was able to nurse my daughter until she was 1, and as much as I am up for a challenge things with him are getting a bit frustrating. He gets fuzzy at night if things don’t happen as soon as he would like and would fall asleep after crying nonstop, only to wake up again in less then an hour 😰 at that point I either have a strong let down and he is happy for an hour maybe 2. Or it takes a while for the milk to come down and the same cycle repeats. I pump during the day at least 3-4 times just to make sure he’s getting enough in between nursing. However after 5 months of getting maybe 3-4hours of sleep a night and waking up to a very active toddler I am ready to supplement with formula at least at nighttime. When he was born the hospital game him Similac and he would drink it. Well now I tried to reintroduce him to it and he refuses I also tried two other formula brands (Baby’s only and happy baby) both were a fail. Are any of you supplementing and what brand formula does your baby prefer? Sorry about the long post 😰