I am torn. Do you have any better pictures? The chicken looks wet or something in this pic. I specifically want to see the saddle feather area between the wing and the base of the tale. Long, thin, sharply pointed shiny feathers in this area means cockerel, as does a darker color through the wings. Pullet saddle feathers are blunt and rounded, like all the rest of the body feathers. I'm leaning towards a cockerel, but really cannot say for certain.
I'm gonna go out on a limb and say pullet. I'd expect a lot more comb wattle, tail feather development at 5 months. The body shape being more "rounded" and posture also suggests pullet to me. I'd also think some efforts at crowing should have happened by 5 months