Worried and conflicted

Long story short I’m 16 and I met this guy at my cousins birthday party back in December (same age) and we got along and we followed each other on Instagram but haven’t spoken since. He recently posted on Instagram saying how much he hates himself and he’s done it before but not when I was following him and I’m kinda concerned. I’m thinking of dming him and saying:

Hey idk if you remember me I’m __ cousin, we met at her birthday party. I just saw your last post, are you ok?

Should I even dm him or is it too weird? If I should though should I say this or something else?