220 lb and Miserable 😔

I've recently noticed a major increase in my body fat, so I checked the scale and found that I've gained 20 pounds in the last 2 months. I got a new boyfriend (love of my life) about 4 months ago and he is always taking me out to fast food places. Especially lately, because he knows I love it. I live with him so I cook for him too. But it's mostly fried foods and pasta. He says he is willing to help me lose my "imaginary" weight, and that he will do anything in his power and support me through b it all. I want to lose 80 pounds. I have two kids, guys. I have to be around for a long time with them, and this is not the way. I just have no idea where to start, I can't ever stick to a routine or an exercise plan. 😭 Any advice or tips would be amazing. Thanks!!