Why is there something moving under my skin?

I can see it and feel it, and don't say I'm imagining this cause I showed my friend Jerica and she saw it to. Anyways, let me explain…it's sort like something is moving through my arm and i can actually see my skin hop up and down when its doing it. It usually happens in my arm, in the muscle area, and I can feel it in the back of my thigh sometimes and ONLY two times it was moving in my eyes and i felt it but i didn't care but my friends are the one who brought it to my attention they said it look like I had an eye twitch. I told people and they joke around and say I have a tapeworm that's why I eat so much and never gain wait but I'm serious…I saw someone on google talking about a blood clot so…what is it? is it even serious?