What should I do? What type of illness is being diagnosed?

My boyfriend talks to himself. At times he would laugh out loud when something would be funny but he would really over do it. it could be silence & he would laugh. He also giggles, or have smirks on his face. you wouldnt know unles you look at him. its like youd have to catch him doing it off gaurd. He know that i am aware of the odd things he do. He is aware himself. One day we smoked, and he got to start talking to himself, having smirks on his face. He even smacked me out of nowhere. when the high went away i asked him why he do that, he stated ” i kept calling him stupid” when i never said such thing. i asked him again he said ” i was talking shit” but like i said i never said anything rude towards or about him. He even trembled a little while talking & smiling that day. I know nothing was wrong with the subtance(marijuana) because i smoked majority of it and im very fine! healthy as ever. he only had 5 puffs. however on a normal daily basis, he talks to himself, laughs, he have blank stares as well, when id catch him blank starring id come close to him, get in his face and softly ask “Whats on your mind? hed say “you” or nothing! sometimes he cant think straight, like he be over thinking. he a even tell me “im getting irritated. id ask whats wrong, he a tell me but sometimes i tend to get a feeling something else is wrong and what he told me is a cover up from what is really wrong. i thought he could have schizophrenia but what i dont understand when we talk his responses actually makes sense. he dresses well, hes in school & work. he keep his hygiene up as well. though i feel somethin is seriously wrong with him. he feels something is wrong with him. but he wont speak on anything unless i do so. but i always sugarcoat because i dont want to be directly forward only because i cant predict how he would feel or react. we’ve been dating for 2 years & 2months now. this just started going on this year 2016, the talking to hisself, laughing outloud etc. he doesnt really have friends, he always hung with his older brother and like 2 or 3 of his friends. I love him dearly and is very concern. A 17 year old is to young to suffer from a mental illness. Btw he doesnt smokes, he doesnt drink as well. He stopped smoking marijuana a very long time ago becuase his head would start hurting afterwards. No one is moving fast enough to get him seen so what can i do?