Are vaginal pulsing contractions a sure sign of an orgasm.

I havent been able to reach orgasm that i know of. And i figure they are one of those things that youll know it when you feel it. But im wondering if they are just way more subtle for me.

This is what happens: ill be going along rubbing my clit and getting faster and then there will be a really warm feeling rushing towards my vaginal area and it will build up until its almost too much to bear, at which point i have to stop whatever im doing (ive tried just pushing through this part, but its like everything is too sensitive) and then when its done i can feel my vagina pulsing with contractions that fade slowly. I usually feel a little tired after this and sometimes a sense of euphoria. Im just not getting the mind blowing part where its like the tide crashing against rocks or whatever. It will be fairly similar when im actually having sex. The warmth will start rushing and then the pleasure will build up until its almost too much but then it just which is when i usually have him stop. Again he has tried to just keep going but everything is too sensitive.

Either way is a bit disappointing if this isnt an orgasm i feel like im dysfunctional. I still enjoy sex and masturbation but i feel like im missing out on something amazing. On the other hand if this is just what orgasms are like for me thats a little disappointing because that means i dont get the fireworks...