Feeling uncomfortable...

Okay so when my boyfriend wants to have sex and I tell him I’m on my period he goes “ew gross that’s nasty” which makes me feel like he thinks I’m nasty idk just makes me feel uncomfortable and awkward. Just a needed to let it out I guess and maybe some advice on how to deal with this?

Update: just talked to him about how I felt when he says that and he said “don’t ever bring it up again goodlord” not really sure what to do at this point. He told me it was my fault I felt this way.

Edit: he’s 18 and we’ve been together for two years