My four month seems to get sleepier during the day. he is showing signs of teething. is sleepiness related to teething?

Eating well?: As long as he is eating well enough, i wouldn't worry too much about it. Teething can certainly make a baby out of sorts for a perod of time. A topical numbing gel can help.

Teething: Teething itself will not cause drowsiness, but the pain or discomfort can cause your child to sleep less. That's why teething kids are often more tired. They may be sleeping less because thwy are uncomfortable.