Does Prolonged Bleeding Indicate An Underlying Medical Issue?

i m 20.5 years old n i have getting normal periods occassionally but for last 3 months there is prolonged bleeding for about 19 days n the bleeding is not very heavy its just thread like or clot like pieces hmm n then cycle again started on time. This time i had my periods on time but due to prolonged bleeding (with threads not heavy ) i started to take progyluton. I had Progyluton for 6days but menses doesnt stopped what to do now? is there any other problem?