I'm underweight right now, around 10-15 lbs underweight, The doctor told me to that I should seriously watch my weight and try to gain 10 pounds. I was working out a lot over the summer and Iost around 6 pounds in the last 4-5 months. I'm trying to gain, now. The thing is I sort of need to exercise now to accomplish a time sensitive goal. I have felt lightheaded for the first time in my life recently, got dizzy very easily, that sort of thing. I mean not on the edge of passing out, but I'm a little not okay. How much exercise do you figure I can get away with and still gain weight?