Aw, if you guys have a good relationship, just text him when he doesn't reply. Don't be all crazy about it though like "WHY ARENT YOU TEXTING BACK!", but just be silly like "Babe, did you forget to text me back?", the key is not to be serious about it if you do remind him that he didnt text back. Be Cute & silly. :) Thats how i am with my boyfriend, because he does the same thing. Usually just during school, (we dont go to the same school) but its not a problem with your boyfriend it seems like a lot of guys are like that, its a guy thing. Dont take it so personal though, he probably doesnt even realize he is doing it! Lol.