Why are you freaking out so much? ED isn't that big of a deal, if you get it taken care of and your father has gotten it taken care of. While there are things that are heriditary that can cause ED, ED itself is not hereditary. I do believe that diabetes can contribute to ED, so that may be the reason. It could also be something psychological or any number of things.
Something that you will hopefully learn before you get much older is that being a man is NOT defined by whether you can get an erection or not. My wife recently did an informal survey with the guys she works with and not one of them said getting an erection makes a man a man.
The funny thing about erections is that the more you worry about them the less likely they are to show up, so my suggestion to you would be to stop worrying about it or you will have this problem a lot sooner than you would like.
I agree with Jude29 (but did you mean more likely to show up in the last sentence?) And yes, diabetes can cause some problems with erections. But ED in itself is not hereditary and nothing you should worry about at 17. I'd be more careful and concerned about the diabetes because it can be hereditary. Take care of yourself and don't worry about this particular guy problem right now! And by the way, it's totally common for us to have problems at times with erections and "performing", however, ED is a different thing because it is consistent and always there. So, don't totally freak out if you have a "failed attempt" that happens to all of at one time or another!