What does it mean when if a guy says mhm if you say bet you do like me?

It can mean 1 of a couple of different things.

1. He's being sarcastic and he may not be interested

2. He might actually like you! But may be a little shy

3. He says it care-free, which may mean he might want to use you.. be careful

& 4. Tell him to be honest, and tell you whether he likes you or not. YES or NO, not "mhm".. you don't want to get your hopes up!