i'm 25 yrs old and i've always gotten my period like clock work...until last april. i started getting my period about every 7-12 weeks...and then when i did get it ..it was extremely long like three weeks long.. i just found out a few months ago that i have a problem with my thyroid so my doc says thats the reason my periods are the way they are... but this month i got my period january 4 and i still have it...and before that i havent gotten it since about october....thats not the only problem today im getting these excruciating cramping pains...kind of unbearable ...then then once i pass a HUGE blod clot it goes away...does anyone know why? or has this ever happened to anyone? im kind of at a loss here because i dont know if this is harmful to me...if anyone could give advice that'd be great.