Hi Megan
You are doing everything right so far. you have sorted out your diet and have began doing some gentle exercise great start! In a couple of weeks you are going to feel fitter and healthier and so the advice i would give you is gradually increase the distance you walk. it doesnt matter how long it takes you whether you run 3miles or walk it you burn the same amount of calories. 3months ago i was 132kg I am now 105kg and the way i achieved this was no secret, i just made a choice to spend an hour in the gym every night.
I didnt do anything special for the first couple of weeks, i kept it simple running 8km (5miles) in an hour because i knew that would help my body get used to exercising on a regular basis, the same thing you are doing right now but rather than walking which by the way is absolutely fine, i decided to do a really slow jog just to get my heart rate up a little and provide me with a bit of a challenge. I should also add that i walked and still do everywhere whenever i can, this includes the 6miles to work and back again, I see it as another way to burn a few extra calories. And so I just stuck to that regime for the first couple of weeks eventually i started to feel as though i could run a bit further and bumped the distance i ran upto 9.6km (6miles) and did that for a couple of weeks all the time as you can imagine losing weight I would do this 4 or 5 times a week depending on how my body felt. And then one day i got into the gym and i said to myself im gunna run 10mile today and so i bumped the speed back down to 8kmh and ran (slowly) for 2hours straight. i was elated and so proud of myself and i was probably 120kg at this stage so I was still a big guy which made it feel so much better because i knew some guys half my size wouldnt beable to do that. that wasnt the end of the story however and that elation i felt the day before soon brought me crashing back to reality the next day when i tried to do the same again and failed

. I didnt let that put me off though and took a break the next day on my return hesitant at first as i didnt want to endure the failure i did previously. I attempted the 10 mile run again and not only did i complete the run i did it 10minutes faster than my first attempt, MOJO was well and truly back

. so learning from my mistake of thinking a 120kg man can run 10miles every day, I just did it every other day and gradually increased my speed and bettered my time. I am now 105kg and run 10miles in 1hr20mins 5 times a week, On mondays i play 5aside football and on tuesdays i train with my local Rugby team.
My point being in a very long winded fashion, which if you read any of my other posts i tend to do a lot

, is start slow when you feel like you can handle a little more intensity knock it up and keep pushing yourself to do better. Keep in mind not to overexert yourself I will not go into the details on how i ended up with a lil trip to the hospital you can find that on one of my other posts but listen to your body. You know the difference between not wanting to do some exercise because you cant be bothered and not being able to exercise because you a physically fatigued and need a rest day. Keep the bigger picture in mind what you want out of it and dont cheat yourself if it is what you really want you will achieve it. If you have any questions I would be more than happy to help. Good luck and stay strong.