I'm replying as I'm also up with toddler. Younger at 22 months but like you slept perfectly fine from 7 months till last week.
Suddenly has become very clingy with me. It escalated to the point that I had to stay in the room until he went to sleep but he'd then wake in the night to be held. Then cry as soon as he was put in the cot (we're still in cot stage). Then cry if he woke at any point and we'd left the room.
We've gone back to controlled crying. I hate it but he'd been up for 3/4 hours a night with me or DH constantly comforting him/staying in the room and he still had a horrible night. So we bit the bullet.
It's harder at this age I think as they're more communicative and have more energy to go longer but he's not left for more than 5 mins at a time. We found picking him up each time we went in wasn't helping as he almost reset. So we go in, big cuddle while he's standing, remind him we love him and we're just outside and give him his comforter.
Tuesday night it took an hr to go down and 1.5 hours of being awake 2-3.30 (so better than the previous nights). Tonight he went down in 20 and has been awake for the last 2 hours but not consistently (went to sleep after an hour and I woke him up going for a wee).
I'm on another thread of similar aged toddlers who all seem to be going through it. Must be a regression around this age but it's bloody brutal!
Oh, and my DH went in despite him preferring me and we found this actually helped as he realised I wasn't coming so gave up a little earlier. Whereas he got more upset when I went in and then left him again.