Help!

My DD has slept 10 to 12 hour nights since she was 3 weeks old, maybe getting up only once or twice a night to nurse.

She is now 24 weeks, and starting last night she is waking up every hour! Sometimes more!

Last night she wouldn't sleep til like 6 am with small 30 minute stretches in between. Finally, I gave her some baby Tylenol to see if she was hurting, and then she slept two three hour stretches.

I don't know what's going on with her! Teething perhaps?

She has not had any new foods recently, she is pooping fine with no constipation, no fever, and when she is awake she is my happy baby for the most part. Maybe only a tiny bit more fussy than usual.

She is drooling a lot and is nawing on everything, but I'm not convinced its her teeth? She has no puffiness or anything like that.

She moves around more in her sleep. Then seems startled and then cries. I wait to see if she will go back to sleep, but she turns hysterical until I get her. She then easily falls back to sleep in my arms.

Could it be seperation anxiety? She has been in her crib since 3 weeks, so it seems odd that it would just now affect her. She is use to it.

Doesn't seem too gassy either.

I am at a loss. My diet hasn't changed either.

Thoughts!?