Food Allergies?

Matthew has always had sensitive skin. I have to be careful w/ what wash and lotion I use or he gets a rash immediately. We've been doing solids for a month now and for the most part it was going well. Matthew is my smaller baby but he sure can eat. He loves food and can inhale two or three jars in one sitting. Part of me wonders if that is too much. The doctor says to feed them as much as they want. I think I'll slow down a little. Maybe just slow down how fast I give him the spoonfuls so he recognizes that he's full a little sooner.

Anyway...back to the reason of the post. Matthew had horrible diaper rash two weeks ago and we worked hard to get it cleared up. I'm sure it's due to the fact that he has 3 or 4 poopy diapers a day now from all of this new food. The diaper rash is gone but in its place is a terrible looking raised and bright red rash on his genitals, inner thighs and pelvic area. So is this still diaper rash? Or is it a food allergy? We've introduced a new food every 5 days. All he has had is rice cereal, sweet potatoes, carrots, peas, pears and bananas. Bananas was the latest introduction. Could it be bananas? I really have no idea and its hard to determine b/c his skin is always a little irritated from something. So I decided to just eliminate everything except rice cereal and sweet potatoes (the first two foods) and just get it all cleared up. But..its been days and it doesn't look any better. Not worse but not better. We also just started vitamin drops w/ fluoride so could it be that... AUGHHHH... no idea. I feel so bad for Matthew...poor guy. I'm allergic to everything and its been a pain in the ass my whole life so I hope I didn't pass on this crappy trait.