Weird rash coming up?

[Cajunmama]

I've been getting this rash on my stomach, butt, hands, my eyelids (weird), and the back of my neck. I'm assuming it's an allergy to something, but I have no idea what would be causing it - I haven't been eating any differently, wearing new clothes, or using new soap/lotion/makeup/etc. What kinds of things could cause it? Or, if it's not an allergy, what else could cause something like this? It's not very noticeable but it itches like hell.