What Causes Gradual Gain In Weight Along With Headaches?

hi, over the past month only, I ve gained a stone and a half in weight, from size 14 to 18-20 I haven t eaten any differently, in-fact, viewing the weight gain, I began further exercise, but it still creeps up very fast. my abdomen is feeling uncomfortable like it has an elastic band around. after eating breakfast in the morning, I have a predictable headache. stinging eyes-irritation like sand, starving and craving sugary foods then when I eat, I start then don t feel like it, I get really tired, sluggish and light headed ready to sleep. if allowed, I d sleep about twice a day for lack of energy then broken sleep in the nights. I have discovered lumps in the top of my abdomen that are prominent in the stomach area. I am trying very hard to exclude any fatty foods. my basic day would include porridge for breakfast, sandwich then for dinner and light meal for tea which would fit on a side plate and I cant finish. my main worry is the weight gain and constant tiredness