I have this exact same problem so I can't say much about the getting distracted part. It probably doesn't help that I'm only a sophomore in high school and have a job to focus on as well, but it helps me to make a list of things I need to do for the game. I haven't finished any jams yet because of the same reasons as you (most of them were under a week though) and all I can say is good luck!
hehe, to go with my notebook this time I also bought 3x5 cards. My plan is once I get a rough idea of what needs done I am going to put each function I think I'll need and a basic idea/simple code with it and then, ideally, I can just go through each card one at a time and when all the cards are gone I 'should' have a game :P
And thank you! :D