Yes, it's normal, please relax.
Your body is just telling you it needs to rest in order to heal. Listen!
I am so sorry you have had this relapse. I guess the one positive thing that can be said is that at least you know your way back from this.
As you have just started your treatment, perhaps you will see some improvement in a little while. Detoxing can help a lot, if you aren't already doing that.
You won't feel like this forever, promise!!
Keep us posted on your progress.