42 yo, 5'6" and have gained 15 lb in 2 years

I think it's stress and metabolic and the fact that I have been working from home for 2 years. I've gained 15 lb in 2 years and believe me it comes on suddenly - like 7 lb have been gained just since April. I never did exercise but now I know I have to, so I've begun. I weigh 139 lb and have a bloated belly and it has been bad for the way I feel and look - I don't fit into anything any more and I just feel generally ugh. So I've begun a restricted diet and a 45 minute 3.5 mph walk at least 3 days a week - I cannot manage everyday - yet. Hope to share my journey with others. PS: I live in India. I think bad air pollution has a bit to do with this, and stress.