What Causes Muscle Twitching?

Hi, I have been having muscle twitches for the past month. It started off slowly, in my thighs only a few times a day and has since increased all over my body - arms, legs, back, neck, feet and every few minutes. No pain, and no other symptoms. I am starting to get concerned. I am a 26 year old female and healthly. No serious medical problems. I am 5'2 and weigh 95 lbs, and have a healthly diet. Any answers for me??