What Causes Heavy Bleeding During Periods?

hi i am a 46 yr old female. i did not have my period for 4 months. i got it 3 weeks ago 2day. i'm flowing heavey when i get cramps i can feel the flow and when i pee all i see is blood..i have few clots that are small. i cannot see a doctor until monday. what should i do and what can this be?