HELP, kinda young too worry about a baby but am i pregnant?

OKAY, well my last period started on march 2nd.(36 day cycle) had unprotected sex on march 29, (only cause i thought hed stay) & on april 8th i started getting this brown stuff i had it for about a week, so it ended on 16 or 17th, then this week i just beeing having regular discharge but still no period. my booobies sometimes give this pain and itll hurt or tingle & iget a quick headach hear and there, been BEYOND gassy (tmi?) & iget cramps on my left side of stomach (feels like its tighting or if i pulled a muscle) or in the middle or lower, helllppp ?