My body is being weird!!

I started my period a month after my 13th birthday. Since then I haven't been keeping up with my period. I know I should but I don't know ow how. It's really confusing. I don't experience painful cramps like my mom I don't feel anything. So its like this period thing is a shot in the dark. Also I'm late. I haven't been very close to boys ever since I started it seem too risky. So I know that I'm not pregnant at all but it's too late I have the period cycle set up and everything I'm 8 days late!! What Is wrong with me?