You'll feel much better by week 3. First time and this restart time, i was totally knackered all the time but by week three, that goes away.
I'm in week 3 now and I'm feeling fine - even had the energy to go to the gym yesterday! I still get tired a bit earlier than normal in the evening - I'm off to bed at 10 instead of 11 as usual, but that's not a bad thing!
Keep going - you'll be back to your old self in no time!