I am female virgin, so i dont exactly know how sex feels. i was once reading a book that had a sexual scene in it, and i felt my heartbeat in my butt area. is this the climax or orgasm? or is it before that? or is due to anxiety? plz help?

It was likely a normal reaction to sexual excitation from watching an erotic image. It could be the way you may experience orgasm, but is unlikely. Visit the following for information: https://www.webmd.com/women/features/female-masturbation-5-things-know Wish you good health! Get HPV vaccine.

This sensation is unusual for sexual arousal. However everyone reacts differently so it could be. It is not climax or orgasm.- from your description.