Happy to sad in one day

My son was just laughing up a storm the other day and now is crying uncontrollably, won’t smile, & won’t laugh.. I had to walk out of the store yesterday bcuz he went from content to screaming in 10 minutes...

However, with his sleeping; he’s been sleeping from 8/9pm-540-630am straight (EBF) he just has a hard time initially falling asleep (takes us about an hour or more) & he never use to be like this.

Is this the next leap?

He will be 4 months on the 27th...

He also has been drooling a lot and biting down on his hands and toys more... I want to say he’s teething but idk.

He also had a 99.5 temperature yesterday