Help! Baby sweating and is hot!

Erin

I’m in Houston it’s 12/30/17 My son is 3 months and 10days and as of lately he has become more uncomfortable. We hold him and he becomes so hot and sweaty. He’s only wearing a light onesie and I have the fan on in the room. Checked his temp and it’s 97.6 so no fever. I’m just so worried that it might be something I’m not aware of. He has a full head of hair too.