Son with foot fungus

Hello everyone! So I’m kinda lost on what to do. My son is 4 and has nasty foot fungus. Does anyone know what this could be from? We’ve tried multiple different athlete foot creams and NOTHING works. I’m starting to get seriously worried. His toe nails are different colors, rough, some die and fall off. Has anyone experienced this before?

Edit** we’ve taken him to the doctor and all they do is give us over the counter anti fungus cream that does NOTHING