Irregular cycle - please help!

All my life I've been very irregular - I'd get my period one month, get it again three months later, get it a month later , and then maybe two or three months later again - it's always been like this (I do not take birth control). Since early February of this year I have started to get my period every 16 days, not a day less or more. Getting my period twice in a month seems a little but too much and a bit scary. I have to schedule an appointment with my gyno and get it figured out. Has anyone experienced this? If so, why? Your help is appreciated.