What Causes Prolonged Periods Along With Large Blood Clots In Vaginal Bleeding?

Hi. I have been on my period for 12 days now. For the past four days I ve had blood clots that are very big. Just now I went to bathroom and my tampon was out with somethibg attached to it. It looked like very long tissue that looked blue and red. I m 42 years old and I m not on any type of birth control. Do I need to go to the e.r?