I know I don't really know you that well so maybe I'm not the best person to comment, but I don't think anyone sees you as a whinger or a burden. Personally I have really admired your determination, and you have been a big inspiration to me. If people choose to think negatively about you, don't worry about them! You are doing this for YOURSELF, you are the one who matters the most. I believe you can do this, and you have shown that you can in the past. Please don't give up, you have it in you!
I understand that you feel pretty down at the moment, and maybe you can take some comfort in the fact that everyone has days like that. It's completely normal and natural, and nobody every said that this was going to be an easy journey. Please don't give up, you have plenty of support here, and I truly believe that you'll only end up feeling more down if you throw the towel in now.
Perhaps you could focus on making small, easy to manage changes? If gym isn't working out at the moment, maybe you could just go for a walk instead? Fit in a tiny bit of exercise whenever you can manage, and it will all add up. Don't be scared to reach out to people and admit that you need some help, we all do sometimes.