Size 9 to Size 18

I was a size 9 before I got pregnant with my son in December 2016. I had him August 2017 at 215 pounds. 3 months postpartum, I was at 185. I must admit my eating habits suck and I didn't put much effort into exercising. I had every excuse in the book, but I did not think I would get this big. July 2018, I moved out of my family's house in size 14 jeans. In 6 months, I went up 4 sizes. Now, I want to eat healthy and get active but I don't know where to start. I don't know how to stop eating junk and drinking pop. Right now, I could care less about the size of my jeans because I'm TTC. My goal is have a healthier lifestyle. Any advice?