What Causes Discoloration Of Skin Around The Mouth?

I have a yellowing of my skin around my mouth. I have had weight gain. 15 lbs to be exact. I workout 60 to 90 minutes a day and eat healthy 90% of the time. I weighed 125 lbs last year and I now weigh 140! My diet and activity level is about the same. I have also not had my period in 4 months. I am not pregnant. I do not know what is going on.