What Causes Delayed Period While UPT Is Negative?

I am 30 years old. I saw my period on Feburay 17th, them march 18th. At present am suppose to see it on April 16th. But uptill now, I have not see it. Presently, I will have a feeling as if it will come , but is not coimg. when i check my self i will notice a drawing discharge,as if i am in my ovulation. presently is going to 38 days cycle, inside of 31 days cycle. I went for pregency test using blood sample it was negative. pls i am normal