If the body's natural temperature is about 98 degrees (F), why does it still feel really hot when the ambient temperature is 98F?

Probably not I'm sorry. Sweating enough so that the sweat evaporates as fast as it excretes from your pores is optimal. Skin being more wet doesn't cool faster (drops of sweat falling off you don't cool you), so excess sweat would just dehydrate you faster. Sorry