I do a lot of cardio, running 60 mins 4-5 times a week. I drink a lot of water. About 4-6 oz before work out, aprox 30 oz during work out, and 6-8 oz after work out. I notice my stomach actually expands after work out and somewhat remains that way for a while. Does anyone know if working out makes your body hold on to water?

That sounds somewhat normal to me. The bloat shouldn't last for long though.

It should do the opposite provided you continually drink lots of water. When there is a drought (varying degrees of dehydration from inadequate water intake) then you will hold onto water. Otherwise it will help hydrate your muscles and serve as a carrier for electrolytes.

Speaking of, are you drinking distilled water? Distilled water can sometimes sit in your stomach as it requires your body to release electrolytes in order for it to become ionized (not good).