I'm 18+5 and have been getting bigger and bigger. For the past week I've looked bigger than my neighbour who is 26 weeks. I've had lots of movement for weeks now. Had my scan last week and he was happily snoozing and everything was fine.
Yesterday I woke up and my huge bump had gone! 
Today it's still gone. Where's he gone? I know he must be in there somewhere as there have been no problems which would suggest anything else (and at this stage I think I might notice). Where ever he's hiding, I can't feel him move any more. I'm a little bit worried, but more perplexed than anything else.
Anyone else have similar at around this time.