how do you know if your pregnant?

Elle
I can't go see a doctor 
However I finished my period on the 12 th September and had sex that night and then again on the 16th I then kept bleeding after that  I'm thinking I just didn't finish my period the first time and having sex pushed it up again? However I have clear discharge (which is normal for me to get before my period and plus it's my fertile stage) but I have a strand of blood in it 
Never has he "came" in me so I can't be pregnant it's just weird and need someone to talk to ! Xxx