Needed no fails this quarter to get financial aid, got one F, how to approach professor for a D-?

I know there are a lot of problems with my other grades and everything. But I graduated salutatorian of my high school, with ample leadership positions and it was just a really difficult transition to college, when everyone is as smart, if not smarter than you. And to a quarter system where you only have ten weeks to learn enough material for a year, where you take a midterm week 3, get results week 4 and then have to take another midterm for another class that same week. This continues until you get all your results week 10, and when you really need a break, it’s time to study for finals.
I’ve had a harder time than most adjusting to this, and along with other personal problems, I know I haven’t been doing well in school and it appears I should just switch out of my major, or even just take the not college route.
However, being an engineer has been my dream. I had an internship over the summer working with medical devices and I can’t imagine myself doing anything else for the rest of my life.
Right now, I just need advice on how to best approach this problem, not the problem of my life choices. If it doesn’t work out, so be it and I’ll take out loans, but I’m still trying and just seeking advice, so please, only relevant answers.