its time to change your lifestyle .. i know you said your chubby thats mean you are not physically active in sport or any outdoor activity. So this will be very hard for you to suddenly change . From meals (the hardest part) and physical activity but you have no choice . So start immediately write down you plans ,activity and start doing it. For you medical condition please go check with your doctor or get another opinion asking US in forum will only do more harm than good(mentally).