I can't take it anymore

My toddler who is 18 months excessively cries all day long and still wakes up crying at least 1-2 times a night and somedays I seriously can't take it. It's basically non stop all day long with no break except naptime and bedtime if he feels like sleeping through. He's finally at the age where he's going to be evaluated by an OT, but that's not for another 2 weeks and his pediatrician said he might not even qualify for OT 🥴 we've tried everything to make him happy. Keeping things low stimulation, high stimulation, plenty of set activities, free play, you name it, we've tried it. He's plenty fed and hydrated but nothing I do ever seems like it's enough. My first was super whiny and uncomfortable for the first 6 months because he had reflux but he was fine after he grew out of it. But my second, it's just been non stop since he was born and I've honestly given up. He didn't even like to worn as a baby, he'd just scream no matter if I held him or put him down. I hate feeling like everything I do isn't enough, I feel like i fail him every single day because it's a constant battle. It's exhausting. I feel so defeated.