The NHS recommends 3 types of fitness work for optimal health - moderate cardio exercise for c 150 mins a week and then strength based exercise/resistance training and flexibility work, each of which you should do I think 3 times a week. Walking can count as moderate cardio exercise providing you move at a brisk pace, not strolling or stopping too much, enough to get you mildly out of breath - sounds like your walks qualify for this element so you are doing great there. However do you do any strength or flexibility based work? Strength work doesn't have to be lifting weights in a gym, even things like carrying heavy shopping home can count or you can 'home make' some weights to start with by using bean cans or similar, or you can do exercises which use your own body weight such as squats, but you do need to do it right for it to be effective - the NHS has some links to some good beginners strength and flexibility online video classes you can look at to get you started?
Walking is really good cardio exercise as its low impact on the joints, happens outside which is good for mental health and also vitamin D absorption and is free and requires no particular equipment or clothing other than sensible shoes, so don't stop that. However from personal experience (and increasingly scientific evidence backs me up), if your main aim is to lose weight or tone up, I don't find any kind of low impact cardio exercise whether walking, running, swimming or cycling very effective, you have to do so much of it so regularly to make any significant difference that it's near impossible within an ordinary person's time and energy availability - diet control is far far more effective than exercise for weight loss in general, but the most effective kind of exercise is interval training, as high impact as you can get - known as HIIT - there's lots of ways you can do HIIT including doing short bursts of running or cycling sprints, but I tend to use 5 -10 min 'fat burner' shred, aerobics type videos, Michael Moseley made a whole programme on the topic and has a good 10 min routine recorded via the BBC, I've dropped off the wagon a bit with it recently but I think it's something like 1 minute doing as many star jumps as you can, 1 min rest, 1 min doing as many squats as you can, 1 min rest, 1 min running on the spot as fast as you can, repeat? Pretty painful whilst doing it but it seems to work, you certainly get out of puff and sweat (a lot
) but at least you know it's doing something and motivating to increase your 'count' week by week?