Relationship issues...

Cair • 👌🏼✨
So my bf and I have been together for almost 6 months and it's been a long distance relationship this entire time, he lives three hours away. We try to see each other every second or third weekend and everything was mostly great. 
We used to get along very well and be constantly texting, calling or skyping in our free time, but for the last two months he's been a bit 'down'. 
He barely texts me anymore and every time I've bought up the topic, he's dismissed everything I've said and told me that he is fine. We're both very touchy around each other now and he hasn't spoken to me for the last week other than to text 'hi', and then 'fuck it, nevermind' when I didn't respond quickly enough. 
He's a really great guy and everything to me but I don't know what to do. I don't know how to help and it hurts me when he pushes me away. 
Soz it's so long, can someone please help me out?