The first two weeks, it’s likely you’ll feel iffy in one way or another. Unfortunately they’re one of those meds that make you feel worse before it gets better.
I’m on day 7 of mine and I’ve been really tired too. I’ve found that trying to get more energy from food helps. Every time I feel tired enough that I could nap, I have a snack and then it starts to get better (but try to stick to healthier, slow release energy foods rather than going straight to sugar, it’ll make it harder to stop snacking when you no longer need to). Fresh air from outside and lots of light also helps.