Your problems seem to be rooting from a lack of motivation, which probably is due to low self esteem, confodence issues you might be having, since you have mentioned your weight here. It is very easy to get stuck inot this vicious cycle of low view of self body image, feeling depressed about it, resulting in decreased activity, and so on.
You need to break through this cycle by mentally overcoming this obstacle, and consciously involving yourself into physical activities. You have make some form of exercise as your daily routine. It can be anything you like (Gymming, ruuning, swimming, cycling, anything). While you are doing this, do not go with thoughts about people's judgment on your appearance or stamina.
Don't think too far. Keep short term achievable goals. Maintain a diary to make sure you achieve these every day goals.
If you aren't able to follow this and help yourslef, consult with a health professional. They will guide you.