Am i crazy?

I think im pregnant.
I havent even had a missed period yet tho. I just have a 'feeling' that i may be pregnant.... not that it is much to go off.

My last period was on the 9th of March.
I had unprotected sex on the 21st March.

My periods arent regular as i have just recently come off the contraceptive pill about 3 months ago, so i haveno idea when my period is due.
I did a home pregnancy test on the 30th of March which was negative.
But im still convinced im pregnant and it was just a false negative coz its too early.

My symptoms thus far are:
Extreme lethargy...always tired and have to have a nap everyday
Frequent urinating
Cramps every now and then

can someone please tell me what i should do.
And when the right time to take another hpt would be?