What Causes Acute Vaginal Wetness With Squirting?

when I met my wife she was a virgin, we've been together for 7 years. The sex has continued to get better year over year and her orgasms have continued to get stronger. In the last six months the wet spot in the bed has gone from small and sticky to 15 inches across and it soaks the bed. When she is on top she literally squirts a stream of ???? 3 feet across the bed. I had other partners before her and I know this is not the norm. My question is;
What is the fluid flying from her body?
Where is it coming out of? (when it happens she almost goes into a convulsion) (dont get me wrong, we love her orgasms, we just dont know if we should start wrapping the furniture in plastic)