Can’t seem to orgasm

So sorry for sharing too much information but I just got my first vibrator. Super excited but every time I try to use it, my body seems to get too sensitive. I don’t think I’ve ever had a proper orgasm, but every time I come close with the vibrator, my body seems to get really tense. I just feel like there’s a stop sign right before the finish line. Any suggestions or ideas why this is happening?