3 yr old terrible sleep

We have a three year old that potentially has adhd (too young to diagnose officially but his dad has it and a lot of the signs are there). Since he was two he’s always been difficult to put to bed. We’d have a consist bedtime routine, he wasn’t overtired, checked off all the boxes of all the tips u see online to get him to sleep. But he would still play around or toss and turn in his bed for an hr, sometimes 2 hrs, before falling asleep. Now that he’s in school, he’ll go to sleep much quicker, but there are some nights where we have to give him melatonin just so he can fall asleep. Even tho he was hard to put to sleep, he would at least always sleep thru the night. Now lately he is waking up in the middle of the night EVERY NIGHT, just cuz he’s trying to get into our bed to sleep. I don’t wanna reinforce this and let him it’s okay so we try putting him back in his toddler bed and I watch him on the baby can actively try to fight off sleep. I don’t think it’s cuz of nightmares or separation anxiety. I really just think he doesn’t like sleeping lol At my wits end here cuz it’s really starting to affect my sleep. I’m tired all the time. Idk how to get this kid to start sleeping thru the night again.