Really need help

I need help and I don't know where to turn, I was 12days late on my period, I did a test from tescos (after doing the test I have read the reviews and everyone has said the same and it's crap) the test came up negative 2days later I was spotting for a day but very very light, and then it stopped again, I still wake up every morning feeling sick and tired and then buy mid evening I'm feeling ok again, I feel sick most of the time and I have horrible back pain, I don't know weather it's worth me doing another test or it's just nothing due to spotting. 

Thanks