Does Crypto commonly come back?

Pardon me for Chapter 138 in my stomach parasite story…

Quick recap for those of you not hanging onto every detail for the last eight months…
-In April I went to Mexico and picked up the parasite Cryptosporidium
-The initial lab test proved negative
-I suffered for several months while it grew and multiplied
-In October I did another lab test, which was positive
-I was prescribed Nitazoxanide which helped.

Now, the symptoms are coming back. I had such a bad case that I wouldn’t be surprised if it fought it’s way back. Is this possible?

Unfortunately my gastroenterologist is making it really difficult to get tested again. :(

Thanks!