Hi Meagan,
I don't have cf (my daughter does) so I haven't completly been in your shoes. But, I have bee you age and trying to deal with a lot of stuff, and I have been depressed. There are two things I know for sure:
1. It will not go away or get better on its own. You may not need meds, but you do need someone to help you start sorting things out. For me, seeing a therapist was the kick I needed to get my stuff back togehter. Basically, it pissed me off and that gave the motivation to do something aobut the cause of my depression. Your scenario is totally different, I understand, but in some way, you need to reach out to a professional, at any cost.
2. You dad is you dad. He loves you and wants you to be happy. Regardless of his emotional issues or his inital reaction to learnig that ;you are depressed, he has your best interests at heart. You owe it to yourself and to him to talk to him about this. I was reluctant to talk about my depression with others, too. I was afraid of being judged, pitited, rebuked, ignored...but, once I mase up my mind that something had to be done and I started asking for help, I was given so much unconditional support from those that I love the most...and that alkone really started to make a difference for me.
I will keep you in my toughts and hope that you can find some way to make some changes to this current situation. It is not easy. It is hell. You deserve better.
Take care and update us. I'll be checking in on you.
Best wishes!