when did your babies start teething???

My baby girl is 4.5 months old. She has always been an awesome sleeper, only waking up once through the night. Ever since she turned 4 months she has started moving around all night not comfortable. I wake up a lot to tap her back to sleep and get her comfortable. Today she is not a happy camper. She is so tired trying to take a nap but keeps whimpering every 2 minutes then waking up screaming like she is in pain. She had tears and all. So sad😭😞I checked her whole body to make sure everything is fine but she still keeps doing it. She has also been drooling lots since 2 months old. I'm wondering if she is teething and that could be the reason for the sleepless nights? My son never started until around 7-8months.