Hi ,if you have only had him 3 to 4 days he may be still adjusting, some of them go through this and others eat the first night home. And if hes a juvenile 3 to 4 days isn't to bad without food. Your humidity I would try and keep around 75% and your heat should be around 82f to 84f, I keep mine at 82f. If his temps are to cold he wont want to eat and if he does eat it wont digest properly and you don't want the food to sit in his system for to long. The heat is very important. Try and put the tank in quiet a room if it isn't because loud noises and traffic will scare him and stress him out, if he gets very stressed for long periods of time his immune system will weaken and he more the likely become sick. Also if you cover 3 sides of his enclosure this helps reduce stress and helps them settle in. Just keep offering and he should eventually take it.