Some people will probably argue with me, but you don't need exercise to lose weight. Does it help? Yes. Do you get added health benefits? Absolutely. But is it truly necessary to lose weight? No. You just need to create a caloric deficit, and you're going to do that by lowering your intake. It's as simple, yet as complex, as that. The way I see it, weight loss happens in the kitchen and fitness happens in the gym (or through other forms of exercise). Personally, I've always viewed exercise as a way of cheating the system because the more I work out the more calories I burn, which in turn means I can technically eat "more" while still creating a deficit. But if exercise is causing you pain, discomfort, or is just all around a miserable experience, don't force yourself into doing it because you think you have to.
That said, perhaps instead of long walks, try starting out small. Take a walk around the block. Do that a couple days, weeks, or however long it takes for you to get comfortable and then maybe try walking two blocks. Just walk five minutes. Ten minutes. Build yourself up to longer walks. It's not a race. The only person you're competing against is yourself, and small wins will lead to bigger victory.
You're doing an amazing job so far! Keep it up!