yesterday i mined dogecoin at multipool.us for about 4 hours at 400kh/s and i get only 250 coins!!

why??
what i should do??

HELP!!
That's a lot less than you should get at that hashrate in such a large pool. Maybe try a different pool over night. Give dogecoin.miners-pool.eu or pool.chunky.ms a shot, see how that works out.
Not necessarily. It's possible in that time they only got 1 or 2 blocks and remember block rewards are a random number between 0 - 100,000. There is no accurate way to judge how much you should get from mining over such a short period of time. 4 hours is not going to make for very accurate numbers.