Is there a six month sleep regression?

Saranya

DD used to sleep through the night until 2 weeks ago. She was rocked till drowsy and laid down. She used to suck her thumb and soothe herself to sleep.

For the last two weeks, she has been waking up very often. The last couple of days, she's waking up every 45 mins.

She cries with her eyes closed, goes right back to sleep if we rock her for 5 mins, only to wake up again in 45 mins. She escalates into full blown crying if we don't soothe her soon.

Why isn't she even attempting to find her thumb anymore? When will she go to sleep on her own again?

I don't see any teeth, the doctor couldn't see any either.

Help!