I personally didn't have an issue with this. After my 3rd baby was born, I exercised close to 1.5--2 hrs/day to lose weight before going back to work. I exclusively breastfed with no issues. I did 2 workouts per day, rather than one long workout,...I don't know if that helped?
If you notice that your milk supply isn't as heavy as it once was, you can always scale back. Remember that baby goes thru spurts too...where milk demand is higher: 3 weeks, 6 weeks, 12 weeks are some spurts. Just listen to your body!
Congrats!