7 month old WILL NOT SLEEP

I’m about to lose my mind. My son all of a sudden will not sleep. He is 7 months.

He went from 10-12 hours at night to fighting his sleep for 20-30 mins at bedtime then waking up 10-20 mins after he falls asleep and it takes me 1-2 HOURS to get him to go back to sleep. He keeps dozing off and then keeps fighting it and squirming and fussing. He’s dry, full belly, everything. I have no idea why he started doing this. It’s been 3 nights straight of it. And once I do get him back to sleep after those 1-2 hours, he only sleeps maybe 2-3 hours and he’s right back up and we have to do it all over again.

I seriously feel insane. He’s also been not eating as much lately and is suuuuuper cranky all day. What can I do to help him?

I’m bawling my eyes out every night I am exhausted and frustrated.