When I was in the first year of my PhD, I overcommitted myself as well. You'll find that there is no need to do EVERY other task that people ask you to do; eventually you have to say NO and focus on your primary goal of the PhD.
I understand that at the moment you have many tasks to balance. In my second year I started going to a gym and it really helped me! I found that if I was frustrated at something in my thesis, having a workout helped me dissipate some stress. Perhaps worth a shot.
Always take time each week to do something for yourself away from the PhD - even with your hectic schedule a few hours unplugged from a computer etc. one day a week may help you to recharge.
I hope the conference goes OK and just remember; all these things you do now can be added to your resume :) Good luck!