Recently I’ve noticed that I only have dreams (or perhaps I only remember dreams) after I’ve woken up and gone back to sleep. This normally happens at about 5/6am, a good 6 hours after I’ve gone to sleep. All this means that unless I wake up and go back to sleep I can’t remember my dreams. Does anyone have any thoughts on why this might be?
Dunno, but the whole thing you do is like WBTB 
1st of all, you allways dream
2nd of all if you train yourself to remember more dreams you will
3rd of all, WBTB does increase 2 things:
1: dream recall
2: lucid dreaming chance
don’t worry about this dude,
I am exactly the same as you. But on school holidays i improve my dream recall and with practising and writing down your dreams, you will start to remember the dreams u had in the night.
The reason you remember more dreams after this much sleep is probably because the more you sleep, the longer your REM periods are. For example, your first dream of the night may only last 10 or 20 minutes and you probably won’t remember it because if you wake up fro it, you’ll fall right back to sleep, but in the morning after 5 or 6 hours of sleep, your dreams last up to 90 minutes, so if you awaken from one it’s likely that you’ll recall much of it, rather than falling back to sleep before getting a chance to remember it.