What causes sensation of ant biting on various parts of my body?

Ants . Or delusional parasitosis or stimulant (amphetamine, methamphetamine and cocaine) abusers with formication (a feeling that ants are crawling on the skin) - self-inflicted skin lesions from an imaginary infestation is not uncommon. More often than not, psychiatrists are able to see these better than your regular doctor.