What Is The Reason Of Heavy Bleeding And Clots During Menstrual Cycle?

Hello, I started my menstrual cycle on time saturday and did my normal routine with alternating between tampons and pads and into my second day I was bleeding heavy while wearing tampons, so sunday night I came home and changed my tampon out and over to a pad. I fell alot of blood being expelled from my vaginal area and just figured I was having a heavy period this month. Well around 3am, I went to the bathroom and noticed alot of large clots that were coming out. I then became very concerned and got very little sleep that night. The next day my period started to taper off and by monday night I was spotty. Woke up tuesday and notice I started my perion again, very light though, but passed another clot, this time dime sized compared to the other night. Is this a normal occurence? My periods are usually normal without as many clots as this time. Could my tampon been the reason for the large amount of clotting? I am 35 and my mother seems to think it is my body changing since I am getting older. Thank you for taking your time in reading this.