I missed my period but had light brown discharge for 5 days about a week after I expected it to start. It's been 9 days since the discharge has stopped. My normal period is going on 3 weeks late. I think it was implantation bleeding but my tests have come up negative so far. I'm 23, no meds, no health issues that I know of. Has anyone had this but ended up pregnant?

It is very possible, two options, wait till the next period due date and do another test if you do not get the period. The other visit with your doctor for a more exact test.