First get a medical check-up.
Your body mass index should be about 22.5 with a body weight of 180 pounds. Therefore you are lugging around 100 pounds of more weight than you need. It’s no wonder that you have no stamina. You must realize how important it is to maintain good health though regular physical fitness, and healthy eating habits (eliminate junk foods and eat foods recommended by NIH). Also discontinue recreational drug and or alcohol and tobacco use.
Join a fitness club and start exercising a little everyday (not a lot once in a while). Keep a fitness journal to keep track of your progress. Write in it daily all the exercises (sets and reps, miles jogged, walked, swimming etc). If one part of you body gets sore or injured, then workout the body parts that are OK. Concentrate on getting stronger first and then slowly work on losing weight. It is not easy. Maintaing good heath takes perseverance and a lot of hard work. That is why there are so many unhealthy people in the U.S.A. and that is so sad because most of the poor health is preventable.
Believe me if you just let yourself go, then you will be in a world of hurt health wise by the time that you reach my age.
I’m 5’ 11”, 155 pounds and am 60 years old and jog marathons and participate in triathlons (I’ll be jogging the Boston marathon 2011). I’ve kept a fitness journal since 1983. The record shows that I’ve run an average of over 3 miles for every day that I’ve been alive.
Take action today! You can do it! Start working on being fit for life. You may not live longer but a strong and fit body will get sick less often and less severe than a weak unfit body. Also you will reach old age being stronger, healthier and more active.
Good health!