That thing called "Slender man" is an urban myth. Adolescents made the whole tale up to scare the gullible. It took off because people believed it when others pulled pranks and tricks on them, captured supposed footage and pictures, uploaded all this nonsense to the Internet, and it went viral. Sadly, many took this all quite too far. There were accidents, people going mental over it, and deaths. Seek professional therapy or visit a physician to explain your concerns. Symptoms like anxiety, paranoia, hallucinations, and stress should not be ignored. It doesn't make you weak or crazy to seek help either.