First begin to have Os? Maybe?

After almost 1 years riding, I finally found a possible mark of orgasm. But I got it without any devices.

Before several days, I was sitting on my chair and enjoying the pleasure. I had same sensations as before. But at a moment I tried to be utter relaxed and contracting my PC muscles, I felt the sensation was filling. As some points the sensation climbs no more, a suddenly release with a full-body electric current feeling, pelvis and waist muscles were 'push forward' as a strong shaking.

After I experienced these, I feel I can have this semi-automatic 'clamping' every time. Before several months, I began to have the feelings that my brain became empty and very concentrated on pleasure, it was very good but the feeling falls quickly. Now I feel I can press forward and pass this period, the sensation will be more filled and more concentrated on the inside, and the pleasure also get stronger and stronger. Sometimes I can felt as electric currents gathering on pelvis areas, and muscles were tightened up, the suddenly ‘clamping’ may followed this. It is semi-automatic and I can find something inside is close to erupt and have an unstoppable impulsion to ‘push’ the muscles on pelvis area, the strong clamp will happen if I follow my feelings. But if I still try to force to relax all muscles I will lose it.

I also noticed before the ‘clamping’, It will be a light, short but uncontrollable moaning.
And sometimes after the ‘clamping’ I felt something in my brain were really good and relax, then softy on my bed or chair, but sometimes it is only a spasm with nothing special.

But generally, the pleasure of and after this suddenly spasm is still too light..

Is it a real orgasm feeling?