does my 6 week old look dehydrated?

I know they say look for sunken eyes, soft spot etc for dehydration but I'm a ftm and just can't tell. My baby was put on nutramigen the other day because he has bad allergies to other formulas but I feel like it might be making him dehydrated. I try feeling his soft spot but I feel like there's always a slight dip in it. (Normal or no?) he was very drooly and then we started this formula and now not so much. I've also noticed he doesn't have as much tears when he cries. If he is dehydrated what can I do? He has to be on this formula :( my question is do his eyes look sunk in to you guys? Or his soft spot?