HELP ASAP!! Am I pregnant

Ok so me and my ex had unprotected sex 4 times over 3 weeks ago, it was during my fertile week, I'm 3 days late for my period but yesterday I put a tampon in because I was sure I was going to come on because I had abdomanal pain and when I took it out only 1/4 of the tampon was covered in a milky brown discharge (sorry if that's too much information) but there's nothing in my knickers and I have really bad lower back pain and abdomanal pain, I did a test a week ago and it came back negative I'm so confused?!! I really need help as me and him are not speaking and haven't done since the last time we slept together and if I do end up being pregnant my mam would kill me if she knew I'd been seeing him again so PLEASE help I need all the answers I can get :( p.s I've been tested for STD and all came back clear 

Vote below to see results!