Thanks for the query.
You obviously need to be concerned because any bleeding of more than 7 days is considered to be abnormal.
Considering your age, most common likely diagnosis could be a fibroid uterus
Other differentials include fibroid polyp , adenomyosis
or DUB(dysfunctional uterine bleeding
Get an USG done for diagnosis .
You can take NSAID for symptomatic pain relief and
tab tranostat for immediate control of heavy bleeding.
Consult your Gynaecologist for further treatment plan.
hope this helps.