Help Me!!

hello there,

I dont know how to start these things so here goes, 

i have irregular periods but the latest ive ever came on is the 21st of each month and yesterday i saw a tiny little bit of blood so i generally thought im due on but when im on im on really heavy like straight away but this time its really light literally like a couple of drops maybe even less and ive had a few sign of early pregnancy but im scared that if i do a pregnancy test it will be negitive and i really dont want it to be so any helpers out there please help me? xx