Can’t orgasm!

Idk what to do. I just bought a vibrator and I can be so horny and turned on when I use it..then I feel the buildup, my legs go numb and I start moaning uncontrollably..but then nothing happens. No big release of anything. It just kinda fades away and then I’m not even in the mood anymore. It’s like it’ll take me a minute to get to that buildup and then i try for like 5 minutes agter that and just feel nothing. Why do I suddenly get less horny after that buildup??