I am sorry to hear that you are dealing with this problem! Fungal infections of the toe nails are very common, and they are caused by various fungi that can be picked up in common public areas like showers and gymnasiums. They cause thickening and discoloration of the nails, sometimes also with some odor.
The main problem with fungal infections of the toe nails is that the fungus is actually living quite deep in the nail. This means that anti fungal creams basically never work for clearing up nail infections (although the do work for athlete's foot, which is a fungal infection limited to the skin of the foot). In order to achieve high enough levels of the anti fungal drug inside the nail, it is almost always necessary to take an oral anti fungal medication.
Oral anti fungal medications are available only by prescription from your doctor
. This is because the drugs can have some side effects, including occasionally causing some damage to the liver. This side effect is rare, but it means that you will need some blood tests to go along with taking the medicine.
Talk to your primary care doctor
, who will be able to help you with this problem.