I used to suffer shin splints - not because of obesity, but because of tennis.
I'm going to third the "new shoes" and second the "gel inserts" - you can even try putting gel inserts in your boots if you absolutely MUST wear boots, every little bit of cushion will help.
When I had shin splints, my coach would make me do a variety of exercises to strengthen/help my shins and calves.
The biggest would be sitting on a ground, grabbing a towel, and doing ankle flexions/extensions (pointing your toe, and then flexing the ankle) with the towel around my foot for resistance. Just point and flex the toe, pulling back with moderate resistance on the towel, working up to three sets of ten (I started with 3 sets of five, but you can do it however you need to!)
This might sound REALLY weird, but walking on your toes and heels can help. Start by getting up on your toes and walking ~ 15-25 yards. Then points your toes inward (like you're pigeon-toed) and do it again. Then get up on your heels and walk the same distance. You may have to master just STANDING on your toes and heels before walking, everyone does it at their own pace.
I also used to make sure to stretch out my calves thoroughly. Sometimes shin spints can happen because of your calves (believe it or not) and you're putting undue stress on your lower limbs. So make sure to do that as well!
I bet you could google exercises for shin splits, or walking stretches, to help you on your way
Kudos to you for walking every day, even despite the pain! That's very inspirational! You can do it, and I hope your shin splints feel better soon (they're awful!!)
Female, 31 years old, 5'4 1/2" tall
Starting weight 1/4/11 = 215.2 lbs.
Weight 8/11/14 = 180.4 (net: -34.8)
Current mini-goal: 180 lbs.
Next large goal: 165 lbs. by 12/25/2014
Lowest weight: 156.7 lbs.
150.2 lbs. <--- Official "Healthy BMI" weight
Estimated final goal: 130-140 lbs.
"You don't have to change your life today. You only need to change your day today."