I didn't start feeling pg until around the time the next AF was due. My AF came every 28 days. I used to get sore boobs and feel tired anyhow when AF was on the way so it was a bit hard to judge.
My 1st pregnancy I tested 4days before AF was due (was keen) and got a -ve, I then tested the day AF was due, still -ve, I didn't get a +ve until 4 days after AF was due. My boobs were sore and I was dog tired and got a cold sore which meant I was run down or something was happening. 2nd time round I felt exactly the same, sore boobs, dog tired and again I got a cold sore in exactly the same place. I tested a day b4 AF was due -ve, then I bought a different brand I think it's Fortel (the one where it says you can test b4 AF is due), and the lines came up straight away.

Keeping my fingers crossed for you.