Why do my legs shake after sex even if i dont orgasm?

ive heard a girls legs can shake excitedly after sex if she has an orgasm.. but me and my boyfriend basically started having sex and i havent have an orgasm yet but my legs still shake really unpromising afterward. what causes this? im not complaining roughly speaking it i just want to know why it happen.
Answers:

Natural Birth control.?

Your muscles are just tired. Much close to they would be after any extended period of diversion. It's nothing to be alarmed by.

Is this wrong?

your muscles are tired from have your legs open for so long.

Has proactiv be proven to not work?

I guess it's because of the excitement.Adrenalin can cause many things resembling that :) Don't worry, everything is underneath control - it just resources you really like him, and he make you enjoy everything he does to you even if it's not crowned beside big orgasm ;) My bf's legs shake too when i pleasure him and it makes me run crazy coz i know I'm doing something right ;) Relax, enjoy and agree to it happen...and you can be sure that he is enjoy it too ;)