Muscle spasms, not twitches, occur everywhere!

For the past couple of years, I've been having these weird muscle spasms (not twitches!). They occur everywhere and are about five minutes apart. I talked to my doctor a while ago and he told me that I need to stretch more. The fitness instructors at my gym make us stretch at the end of each workout, though. Does anyone have an idea as to what this could be? I am 19 years old, eat healthy, work out often, and am not a smoker.