First of all, most people are their own worst enemies, because you have to live with yourself, and you know exactly where your weakest points are to emotionally punch. So chances are you're more attractive than you're giving yourself credit for.

Secondly, your body is not static. You can really be whatever you want to be, and if your body isn't in shape now you can get it into better shape, and probably into better shape than it ever was before in your lifetime. There is certainly a genetic and birth lottery for how easy your goals are to achieve, but they do remain ultimately achievable. I personally felt like as a nerd I couldn't choose to be physically active, that I had to pidgeonhole myself into a stereotype, which is very not true.

Thirdly, whether or not you're super hot in reality, getting your body moving is freaking amazing for your mental and physical health, and once you can start hitting milestones your past self never could have its incredible. I literally could never do a pullup when I was younger, but now I can do pullups. And that took literally 2 months of 20 minute workouts. So pickup even a basic 5 day at home workout regiment, or bike every evening or run every morning. Seriously the healthier feeling from actually moving vs. being a lump is amazing

Finally, the bar is so freaking low for dudes. If you can be confident and not a douchenozzle and have decent lifeskills I guaren-fucking-tee you there is a woman out there who is perfect for you and far more interested in that criteria than simply finding someone who's conventionally attractive with social traits that they can put up with.