It is natural that you are apprehensive about radiation
The following facts should be considered to determine if you could have exposed yourself to more than allowable radiation.
It is a routine that patients administered high dose of radioiodine are kept in isolation ward till the external radiation exposure is well within safe limits.
How long did you spend time with your mom after she was discharge? If it was a few minutes to 30 minutes at a time, it is fine. Alternatively, if you slept in the same room as your mom, you might have got exposed to more radiation.
The chances that the radiation you got exposed to, will affect your reproductive system is very rare. Actually, the reproductive system of the person treatment is only rarely affected because of treatment.
I treat thyroid cancer
patients with radioiodine. My advice is to just relax.