Im getting distraught here :( why has he gone cold all of a sudden?

im 17 and my ex is 22. :) we said we would get back together when im 18 which is in a month, we've been saying this for some time. 3 weeks ago i saw him and it was a lush night! he was so happy and i was, and even on facebook he posted ''what an amazing night its always been you <3'' i couldnt see him till three days ago because of my A levels, but throughout those weeks he texted me and was really supportive. the last time i saw him was three days ago. the night started of brilliantly, but then halfway through he fell ''asleep'' like everytime i tried to wake him up he grunted. To be fair he had said he was really tired, and i guess i might've annoyed him trying to wake him up so much, i did it in a friendly/ jokey way though. he didnt cuddle me though :/ again he might've just been too tired. When he dropped me home he said sorry i was just mega tired, and during our convo on the way home he said he was happy because he had me etc. :) but since that night he hasn't contacted me apart from ' pokes ' on facebook, im starting to get realy worried! i texted him yesterday but no reply? :( am i just being paranoid but has he gone off me? i dont understand why? the night went so well till he just fell asleep. im not mad at him at all, its just it hurts that he didn't text back, or even contact me at all :/ maybe he's just busy? what do you guys reckon? im not going to text him again because that would be too clingy. thank you for any responses :)!