This may be weird, but: it's a good thing.
While restricting, your body was in a surviving mode. It did everything it could just to keep you alive. No "time" to get ill.
Now, as you're getting better and better, your body finally has the energy to get ill again!
I know how you feel and I know that you're feeling quite crappy right now, but believe me, it IS a good sign! You're healing. I had exactly the same. During restriction I was never ill. I didn't even catch a flu. After being in recovery, I got ill for the first time in ages, and last month, I've caught two colds in a row.
But you can believe me: as you get more energy while recovering, your body will get healthier and healthier again.
Sending lots of love <3