I think it makes a difference if you are male or female. If you are male, the problem is more worrisome, in my opinion. Also, you don't say if you can't orgasm only during sex or if you can't reach orgasm when masturbating. Have you gon one or off hormonal birth control if you are a female? have you started taking any new drug since then, prescirption or illegal? One other thing- have you been under more stress in the last six months or has something major happened to you since then?
are you stressed out? what's different in your life? my libido has changed but i know its due to my medication & my hormonal imbalance.
you should research male sexual dysfunction just to see if they offer any advice, or give you reasons why this happened.