Is there one?

I'm trying to figure out WTF is wrong with my son. He has been a near perfect night sleeper since 9 months old. Now, he's never had high sleep needs, but what's happening lately is downright absurd. For the past 9 months he has slept 10.5-11 hours overnight with a 1.5 hour nap. For the past month he has refused naps on some days (we leave him in his crib 2 hours and he doesn't sleep but then falls asleep the second we leave the house in a stroller or carseat). He has cut night sleep to 10 hours as well. Nothing has changed except I'm more flexible on bedtime (sometimes will push by 15 mins). He takes longer to fall asleep for night sleep and cries before bed now.

He is utterly exhausted after barely napping all weekend. We tried an early bedtime last night (7:15) and he cried until 7:45 and then slept all night until 6:30. But then I put him down for a nap at 12:30 and he didn't nap until 1:20 and woke at 2 screeeeeaming bloody murder and I left him crying for 30 mins hoping he will go back to sleep but he didn't. Started shouting no sleep and threw everything out of crib. Now he's up but yawning. He was acting super cranky last Friday so I tried an early nap putting him down at 12 and he didn't nap for 2 hours just screamed. Is this behavioral? WHY?

He doesn't have 2 year molars but I don't see them coming in. HELP. Mama is 11 weeks pregnant and cannot handle a toddler who sleeps so very little.