First I'll say, you're not alone! i think at some point everyone worries that they're taking too much insulin, or not eating right, or not exercising enough...
Second I'll say to you and everyone else DONT WORRY ABOUT IT!!!!
You're totally doing great!!! diabetes isnt about not eating sugar, it's about taking your meds so you can eat some sugar.
As diabetics we shouldnt be eating or doing any differently than every single other person should be. Fast food isnt ideal for diabetics... or anyone!
If you are healthy, managing your blood sugars, testing regularly, and also taking care of other health issues You are on top of your game!
How much insulin is "normal" well that varies as widely as any other biological function. take what you need. ofcorse that isnt to say you should take hundreds of units so you can eat a tube of premade cookie dough LOL that wouldnt be good for an olympic athlete, much less anyone else! LOL
You sound like you might be wanting to mae health improvements in your life over all... try starting small. when you head for fast food get a salad and water instead of the chicken fingers and fries... or add an element of exercise to your life... but dont do it because you feel guilty for being a "bad diebatic" do it because you love life and want to live it to its very best!!!!
guilt can really burn out a diabetic, so dont let it have any of your energy, life takes enough all on its own.