How can you tell if you have tapeworm?

I am 13 and I want to know because when I have to poo, not that much comes out or my Large Intestine feels empty. I am an everyday pooper but now i go every other day it seems like. I also noticed that there are 1 in to 1 1/2 in skinny strings of stuff in my poo but my mom said its flem. I am somewhat scared becuse I have an anxiety disorder and my concerns aren't helping! Please tell me whether or not I should be concerned!!!