Period for 3days and Now Brown Discharge?

the title says it all pretty much. I've had my period for three days which is irregular because my periods last seven days. But my period now has changed to three days' YES heavy flow but the 2nd day the blood went down to brown spotting and now im not bleeding at all just brown discharge. I'v had unprotected sex with three of my partners while drinking and i don't know what it is. But I do sleep and eat alot but no vomitting or nasuea or conctepation or peeing alot. this all was in two to three weeks ago? HELP?