Help!!! Exhausted mama.

My almost four month old has been in a routine of waking up at 3:30/4:00am for a feeding and not going back to sleep!! He's also still wanting fed every 3 hours. Over night he might make a 5 hour stretch without a feeding. He gets tired around 6pm. We had a routine of putting PJs on at 7:30 pm and relaxing. He'd sleep 6 hours but that hasn't happened in awhile. But it's always the last feeding of the night/first feeding early morning and he just won't go back to sleep. The room is dark, I have a sound soother on, there minimal stimulation. Ughhhhh