I am in P1 and also workout. Before you try the Athletic Protocol, why not try adding in a 4th packet? I have been working out since day 1, but the first 3 weeks I was pretty weak and had to scale back my workouts. I do Crossfit and run, so my training is rigorous. It sounds like you are getting back into P1 after having been on vacation so you body is adjusting again to the lower carbs and putting your pancreas back to rest. Here is my typical day:
9:00 am- IP packet
12:30 pm- 8 oz protein, 2 cups veggies, salad and 1 t. olive oil
4:00 pm- IP restricted packet
5:30-6:30 pm- Workout
6:30 pm- IP Ready to Drink chocolate drink
8:30- IP packet, 2 cups veggies, salad and 1 t. olive oil
This has been working great for me! Once I got over the hunger of the first few days, I started to feel better. After about 3 weeks, I noticed that my energy levels during my workouts were starting to increase and now I am at or above what I was before IP.
My suggestion to you would be to continue to exercise, just scale it back to match your energy level and add an extra packet immediately following your workout.
You can do this! You have been down this road before and you know how crappy the first 3 days are. You need to just committ to it and get over the hump. Just keep telling yourself "Get through today" and eventually you will get through the rough stuff and be on the other side.