My cat has fleas but will not let me near. ?

He has been living with me for about 3 months but we had problems from the start... He has never been comfortable being in the same room at the same time as I am. .. and he hides behind the wall where it's filthy (I live in an unfinished basement apt.) When I get too close poof he's gone behind the wall. He only really comes out to eat and use the litter... The fleas have recently become unsatisfied with his blood and I am getting attacked at night... HELP!