Where to start AGAIN?

I am 57 years old lost 40lbs. Using TOPS (Take off pounds sensibly). I was so proud of myself, than a ton of shit hit the fan at once my husband at the age of 59 lost his job, than the corona virus shit everything down ect. and I have gained it all back plus more (I haven't gotten on a scale as of yet). I NEED to get back in better shape, my knees kill me, I am winded when walking ect. I am so disappointed with myself it took me a year to lose the 40 I hate to think of how long it is going to take me this time to lose it again.