My son is 3.5mo and for the past 5 days he's really been sleep regressing. Worse than he's ever slept before. We are so tired and don't really know what else to do. Last night he woke up several times but from 3-5 would not go back to sleep it seemed like he was trying but just couldn't. Also idk if I should keep nursing him as I don't think that's the reason he keeps waking up but I'm also out of ideas. Any advice!?