I have alot of discharge after my period (10 POINTS)

Well Im 13 and ive had my period almost 3 yrs and it seems like whenever i end i get alot of slear disharge why is this?also ive noticed the ast few periods i am having symptoms like back aches,cramps the first 3 days,bloated,mean,tired,gy, I used to NEVER have anything why am I getting symptoms now?Thx :)