trying to get my old, fit, body back

Have you tried apps that pay you for exercising/charge you if you don't? I use Pact and after some growing pains, it works well for me. The concept is basically that you commit to exercising x amount of times per week and if you don't, they charge you (you can pick the amount, $5 per missed workout and up). They also have a pact for food logging (syncs with MFP) and a veggie pact.If you complete all your workouts/food pact(s), they won't charge you and you get paid (I get about $1.50/week for 5 workouts and 5 food logs.) So you won't get rich off of it but not being charged is a good motivation! And you can let them know if you have a medical emergency and need to pause and take a break if you need to (starts with the next week).
The workout pact syncs with fitbit and other devices (10000 steps/day count as completing your workout) and has a motion tracker for at home workouts (30min+ counts as a workout). You can also "check in" at your gym with it, if it's recognized by the app (I've never done this since I don't have a gym membership). Also syncs with runkeeper and other apps. The motion tracker can be a bit iffy - if I have my phone in my armband, it only works if I move my arms vigorously (i.e. while running), so during most of my bodyweight/cardio workouts at home, I just hold my phone in my hand.
Good luck!

also it says OP is 18 years old? I'd just like to point out that if you're aiming for the body you had aged 15, it's not gonna happen.