Hey there.
I don't think you're pathetic or filthy, not at all.

I think you might've just found an outlet for your sexual desires perhaps a little too soon, and are having trouble breaking away from it. It's not really unlike someone with an addiction to pornography.
You won't be in legal trouble, but I would not use anyone from Facebook, largely for how...lol I suppose personal...that is. It is illegal for them to engage with you if you are underage, but I don't think you're in any legal trouble.
Have you ever spoken to someone about this, like a counselor or therapist? I think they can help you understand why you do this, and how to ween yourself off it.
Stay strong Wendy.

You're in my prayers, and I wish you my best.
Harley