My first instinct here is that there is nothing wrong with you. My own husband prefers masturbation to sex quite often, and I personally find nothing wrong with that. It could definitely be an ego blow to your boyfriend, though, if he is insecure or measures his sexual prowess on whether or not he gets you off. The concern here is that maybe you don't open yourself up to other people. It may not necessarily be the lack of libido, but rather the lack of trust, passion and desire for intimacy. Sometimes, this is caused by abuse as a child I suggest, as a first step, exploring together everything that makes you cum when you are by yourself. If it is a certain pressure, or a certain fantasy, share it. Make it a part of your sexual adventures. Share your fun with him. Have him run the controls of the vibrator. Explore and learn to be intimate.