Super-O, or just awesome?

I'm having trouble figuring out if what I have achieved is as good as it gets or not.

I have a progasm and have used it twice.

Both times laying on my back in bed with my head propped up and my feet planted on the bed where i could lift myself up, I wait 10-15min and relax before doing anything. Then I consciously contract, sometimes squeeze for a long period, other times quick bursts. It never contracts by its self. Keeping some weight on my legs seemed to be crucial to the experience, It seems that arching my back by pushing up with my legs occasionally helps a lot, I guess that my doing that forces the progasm against my prostate. eventually my body would do this on its own if I kept a bit of weight on my legs.

Both times I was able to get to the point where my body would uncontrollably and almost violently shake (10-15min in). The sensation is wonderful it felt like I was above my bed floating.

The first time I only let this go for about 2 minutes where I would shake for about 10 second periods before I couldn't take it anymore and had to finish myself. The second time I let it go on for 15 to 20 minutes, and eventually got to the point where I could shake for almost 60 second periods but I was starting to get very tired and eventually finished myself. I also kept my eyes closed instead of watching and I listened to music the second time which I will do from now on, it seemed to help me relax more, and the shaking came quicker.

The shaking I have takes place all over my body. legs first, but eventually My back will arch my arms and neck will take part too. However in order to keep this up I must consciously fight to keep breathing and keep contracting and try to keep pushing myself up with my legs a bit, this was the hardest part. Trying to force yourself to breath and perform manual anal contractions while shaking like the girl from the exorcist is very difficult but it was extremely satisfying.

Basically I was expecting an "end" but it appears that what I am getting I could keep this up as long as my endurance would let me. So is this Infinite shaking that I get "super-o" or just the lead up to one and I just need more practice?