Help with the big O

Okay Girls, I'm 22 and never had an orgasm! With or without a partner! Recently bought a rabbit to see if that would do the job and omggg amazing! It's gets me soo close to the point where my whole lower bodies shaking, my pelvic areas contracting and sometimes feel like I need to pee. But I can never get past this stage! I feel like I need to just relax and let go but I can't! Or I stop because it's just so intense! Any tips for me to achieve the big O!! Thanks!