32 on T with No hCG and Arimidex

I started on TRT to improve my bone mass. I have a family history of osteoporosis and had a poor BMD result (I work in Diagnostic Imaging). These results were verified with a physician ordered BMD test. I have had three sets of blood work since January 2013. I am not on any hCG or Arimidex. Testicles are the same size, but seem to “jump” into my pelvis more often. I had a week or two of bad backance, but that cleared up with the Super Miraforte.

1: I want to have another child in a few years. What is my best course of action to ensure I have viable sperm.
2: I am tired in the afternoons and have thought about Modafinil, will this negatively interact with my TRT.