I dont actually know what's happening with my body?

I am 11 days late & I'm not sure if I am pregnant.

I took a test 4 days ago & there was a slight positive. Took a test the day after & there was a faint positive. The day after that was almost not there & I just took a test now (it's afternoon) & I could see a line.

The last time we had intercourse was the 27th January so, I know my chances of a darker positive line is diminishing.

Does this sound really unusual?

I have never had this happen before. I have read about chemical pregnancies so, I am almost expecting this 'possible pregnancy' to end in a period.