Am i pregnant?

I had sex about  3 or 4 weeks ago. I started on birth control 3 days later, havent had sex since. It says im about to start my period tomorrow. But starting about a week in a half ago, ive had cramps & ive been moody. Then i started having nasty chunchy brown discharge, 3 days ago i started spotting. & now its stopped. I know i could just buy a pregnancy test, but i dont want too untill i get the opinion of other people. Does it sound like im pregnant or no??