HELP! Is my 3 year old going through a sleep regression or just getting older? 😭

My almost 3.5 year old was always the best sleeper. For a while his schedule was around 8:30-8:45am he wakes up, most of the time would play in his room quietly for a bit before he came and got me, then at 1pm I would put him down for “quiet time” in his room, where I would allow him to choose to sleep or play quietly until around 3pm. Sometimes he would nap, sometimes he wouldn’t. On the days he wouldn’t nap - bed time would be 6-6:30pm and he would be out right away. On the days he would nap, I would put him down around 8, but sometimes he wouldn’t fall asleep until closer to 9pm, but would still play in his room.

Well for about 3 or so weeks now he’s been waking up around 6am, sometimes 7am if I’m lucky, he’s not napping, he keeps coming out of his room, and he’s going to sleep around 8:30-9:30 sometimes even 10😳 he’s SOOOO cranky and whinny all day. I know he’s tired, but he doesn’t sleep.

I would like to think it’s a regression because this is so unlike him. I always had him on a strict sleep schedule because I found we had minimal tantrums with it and he just needed it. Sleep is important for their development too. So I always made sure he had enough. But this is horrible.

Is this a regression? If so, how long does it last? How was your child’s regression? Anything I can do?