I agree with HealthMan's post, if you think you might want kids in the future, get a sperm analysis done now. See if you have a current problem rather than trying to figure out if TRT caused a problem. Unless you are 110% opposed to having kids, because the future has a way of being unprintable.
Other than that, IMO the critical obstacle to doing TRT by yourself is buying the testosterone ester (any any other meds that require a prescription) without a prescription. Which you indicate isn't a problem in your country.
One other thing to keep in mind, while the vast majority of men will be fairly simple to self direct TRT, you could be one where you have a more complicated problem, then I would suggest a doctor as trying to figure out what is going wrong will be difficult at best.
You could also ask Defy about consulting overseas, do it under medical care for a limited time (6-12 months), then do it yourself.
