I have read your routine. At the moment, you are in a low activity level with insufficient dietary supply.
I need you to increase your protein intake which is a must for everybody. Start eating eggs for a simple solution as I advise almost all people and if you can eat 4-6 eggs daily, it would be better for you and you have to trust me on that. The only thing that you need to keep in mind is to throw away the yokes after boiling them and eat only egg whites.
When you go for your routine walk, start taking your intensity at a next step each time you go. Within a week, start swinging your arms like they do in army parades while walking and keeping the intensity at the same level. That would be difficult for sure but there is no magic pill for fitness. You need to be honest to yourself and do it.
If you can afford it, eat fruits in the breakfast along with eggs. Take meat in your lunch along with fresh salad (salad should be as much as you can eat) and eggs again. Eat normal dinner with eggs a little after you take your dinner. Take a lot of water. If you do the same, you will start to feel that change within a month with a lot of energy and vigour.