I feel you. I used to be so skinny and known for my flat stomach then one day in my 20s especially after moving down south, getting a car and a desk job it stopped being flat.
Now, I got cellulite around my midsection and since I have small breasts, my stomach looks even worst proportion wise. I got a gym membership, discovered dairy makes me bloated even tried going vegan but Im just not consistent.
Thats probably one of my worst traits inconsistency. My only advice is break your goals up into smaller baby steps, take it one day at a time and try not to get discouraged. Get back on the horse as soon as you can. To be human is to err, so dont beat your self up.
I stopped using the scale and use my tape measure or my clothing size, especially since I lift. (I need to do more cardio and better my diet) but anyway muscle is denser/heavier than fat so you can work out and actually gain lbs but look/feel better.