confused period and raising hcg

Emily
I felt pregnant this month, pregnancy tests were negative but I was late, I had blood tests done at work for hcg on 20th at 3 days late and was 2.9 iu/L then later that day I got a heavier AF than I would normally. 
So out of interest I repeated my bloods today to see if hcg was lower as I am questioning if I had a chemical pregnancy and my hcg is 16.6 iu/L! Got home from my night shift just now, PU on a pg test and its positive (faint but defo two pink lines) 
What is going on has anyone had an experience like this?? 
Pic doesn't show the positive line as pink as it is!