The key is to find a new routine that is going to be sustainable.
Can you afford a personal trainer, preferably one with qualifications in nutrition? Ask your GP, you might qualify for a referral to a gym, which makes it considerably cheaper.
If you can't / don't want to go down that route, try and figure out what kind of exercise you would enjoy as a hobby. I used to think exercise wasn't for me because all I had tried was running and team sports in PE class and I hated it. I have now taken up powerlifting and I love it, I look forward to my training sessions and they have become my me-time.
It might take a bit of trial and error, but there will be an activity you will genuinely enjoy, and it doesn't matter whether it's running, Zumba, Olympic weightlifting, salsa or football as long as you do it and like it!
Regarding nutrition, use a free online calculator to work out your TDEE (the number of calories you need daily to maintain your weight) then cut out a sensible amount (maybe 200/300 call less per day) for a steady, sustainable weight loss.
Use an app like MyFitness Pal to track what you eat (don't use the goal generated by the app, replace it with the one you have worked out yourself ; MFP is often terribly wrong with calorie goals). Also, don't be tempted to enter your exercise in the app, the calories burnt are also mostly wrong and give you the impression you can eat back your exercise calories.
Then, rather than a diet, just try and use these calories sensibly. The odd Mars bar isn't the end of the world if the rest of your food intake is nutritious. No food groups should be banned. Base most of your meals around lean protein (chicken, turkey, fish, tofu, Greek yoghurt etc), veg (mostly green), wholegrain, fruit and healthy fats like nuts. The occasional restaurant meal or take away won't hurt if your other meals are sensible.
The best way I have found to make sure my meals are healthy is prep a big batch at the weekend and portion it off, put half in the fridge and the other half in the freezer for later in the week. So for example last Sunday I cooked lots of chicken breasts in the slow cooker with a tin of tomatoes, herbs and a bit of stock. I cooked a lot of broccoli, leeks and green beans in the steamer. That's my lunches sorted (and enough chicken left for a chicken and pasta meal on the Sunday night). I also made a big mushroom and spinach frittata, which I cut into 5 portions. 90 sec in the microwave and breakfast is ready! Hands-on time for the whole lot was about 30 min and I have a week's worth of lunches and breakfasts. In the morning I grab my tupperwares, add some nuts and fruit and take the lot to work. Easy!