We don't have enough information to even guess. Things we need to know (or a VET needs to know ASAP) are: how long have you had him, what do you gutload and dust with and how often, what type of lighting (brands please) do you use, how do you water, humidify, what's your setup like, temps, other stressors around the cage such as other animals, reflections, or lots of human disturbance and is any of this new, and any other health problems he may have had in the past. Chams do puff up and hiss when really upset. Is he trying to bluff to get you to leave him alone? Anyway, if he's acting different than normal you probably need a vet, but we don't have enough info on your husbandry to help much.