I missed my period last month, I'm a virgin?

ok, so I'm 16 and I have had my period for 4 years and nearly 5 months now. I missed my period in Jan.I was supposed to get it around Jan 24th. I'm a virgin. I know that people say that when you're young, you're likely to have an irregular menstrual cycle, but i noticed something odd. When I went to pee, and after I stood up and looked into the toilet (I know this is gross, but please bear with me) I saw little strands of what looked like the lining of my uterus. and i know that women generally shed their uterus lining during their period, but i'm not even on my period. what is happening? Should i go to the gyno or something? Please help!