Too early for this?

Over the past 1 to 1 1/2 yrs, I've been experiencing a gradual intensity of these symptoms: irritability with mood swings, easily becoming fatigued, joint pain (especially upon waking in the morning) particularly in my back/neck/hips, increase in headaches including migraines, difficulty concentrating and remembering simple daily things, limited interest in sex, and lastly my periods started waning. A little over a year ago, I started having periods only last a couple days, then I had some where I only spotted and now I haven't had one at all for several months - at least the past 3. I am only 28 yrs old. Could this be early menopause? Or, are there some other reasons this could be happening?