P waves or O?

Finally had the house to myself and was able to put in my first legit session with my progasm. After about an hour in my pelvic region, thighs and down into my calves began to shake, at some points almost a little violently. It came in waves and happened probably 4 or 5 times. However it didn’t necessarily feel very pleasurable, just kind of a slightly uncontrollable shudder. There was no feeling of warmth or orgasm coming from my pelvic region or prostate, maybe just a little built up pressure on the toy. Anyone think these are p waves and something bigger is in store if I let it go longer? Or is this as good as its gonna get?