Rusty coloured discharge? What is it?

I have sex about 2 weeks ago. 26th may, it didnt go in much just the tip because it hurt me to much due to the fact I hadn't had sex in a year and a half! It only lasted a few minutes not long at all. Now I am having this. Rusty coloured discharge only when I wipe. I had it from Wednesday the 5th of June to Saturday 8th June. It has completely stopped now. I am meant to be due on my period anytime round this point, but nothing. I am having back pain and my breasts are a little sore. They were hurting a lot more about a week ago! I am on birth control Pill but last month it totally messed up so I ended up having 2 periods. One at the beginning of the month and one around the 15th. So I'm lost on when my period is due. I have taken 2 pregnacy test and they both day not pregnant. They were the "clear blue" ones. I am so worried. Could I be pregnant? I really hope not! I am only 17! I do have irregular periods! I Normally start my period 2-3 days after my pill is finished. But I haven't come on at all. I'm so worried I'm not ready for a baby. Can anyone help me to figure out what this is! Please or give me an idea! I am off to the doctors tomorrow and considering taking another test. I am so worried:(