Can emergency contraceptive pill cause a delayed period?

I took the emergency contraceptive pill which induced an early period a few days after taking it (period was early by a week). However I am now 11 days late on my next period. I have been feeling very moody, crampy, and bloated. A home pregnancy test result was negative (taken about 4 days ago). Is this normal and is there a possibility that the preg. test is wrong after so long?