What Causes Dizziness While Masturbating?

Hi. About 4 months ago while masturbating in a lying down position after ejaculation I experienced this weird dizziness, spinning sensation, heard a buzzing sound in my ear too, couldn t even walk straight and I was completely thrown off my balance, it went away in about 20 minutes leaving behind a headache. It then stopped and didn t do that again till another month. I m a regular masturbator (nearly everyday) and as of recently the problem occurs more often, actually every time, I m not sure if this is normal, or of something is wrong with me. Please help