erin, you are not crazy. i have been seeing a blue spot out of my right eye for nearly a year. i don't know what your's looks like, but mine is kind of like i just had my picture taken and the light has faded to that bright blue color. unlike a floater, it is fixed in one spot and moves only with my line of vision, and also unlike a floater, IT IS BLUE. honestly, there is a big difference between blue and black for me, and it sounds like that doctor was just trying to come up with some sort of answer.
i have been to both an opthamologist and a neuro-opthamologist: neither had any answers, and my recent mri which showed no visual signs of tumors, lesions, clots, annuerisms, infections, paricites, or anything else abnormal.
also interesting is this: a colleague of mine told me she also saw a blue spot, but for a much more abbreviated time. she saw her's after she had broken up with her boyfriend and spend hours upon hours crying. i don't know if her's is related, or if so, how, but it was a comfort to know that someone else as least knew what i was talking about!