Don't beat yourself up too much. 60% of jaw growth is done by 5, 80% by 12, and the rest by ~20. The risk factors were likely already in place by that point, you were screwed. In my case maybe because I had a closed bite and it didn't open up until later, which can only be explained by mouth breathing (I went to college 2 years early, dorms were a b*tch on my allergies).
If you insist on blaming anyone, then blame your mother. First, for having the genetic risk factors placing you in the lucky 1/3 of the population. Second, for not breast feeding you. Literally the breast, no breast milk in a bottle (my wife and I are guilty as charged here for our first). Third, for not taking you to the orthodontist at the recommended age of 7 and again at 12. Last, and most importantly, for not noticing your poor nose breathing and addressing it while you were young. It's your parents responsibility to take care of you and that means when something is wrong, they fix it. Either through anti-histamines, flonase, or allergy shots. I'm a little peeved because my mom knew I had allergies and did allergy shots for herself and my brother. It didn't help her but she gave up quickly. She didn't want to put in the hour a week for the treatments (and probably to save the money). Arg!!
So basically your parents f**ked up and you're paying the price now. Maybe your parents never noticed, that's ok. We're all human I just don't think laziness and cheapness are good excuses.