I feel my cycle is getting funny

Well, last month my cycle lasted for 60 days without any reason. I went to the doctor for pregnancy but all were negative. My doctor describe medicine for my period to come, after 1 week of medication, it showed up on this Thursday, so today is 3 days. But I discovered this time my period flow is seem nt so much like before I used to had. I’m feeling it is exactly my period, but seems like the blood stuck inside and just doesn’t come out. Anyone have any experience similar? And should I feel worry about this?