Baby rash

So my little man has had this awful rash for about two weeks now. At first everyone kept saying heat rash but it's only gotten worse even when there is no reason for him to have it. It's not an allergic reaction to his clothes or anything we are putting on him I hate it. It's gotten worse in the past couple of days and has spread to his neck. He seems to have super bad eczema on his thighs and arms and j can't find anything to help that either. What do you ladies think of this rash? And does anyone have anything that helps eczema? His little skin is so dry and cracked I hate it ☹️