You probably need to use a little more HCG. On TRT my LH/FSH was at 0 as well. I was using 250iu HCG twice a week and my loads were decent.
You might need more stimulation to the testicles. Maybe you're desensitized and 300iu isn't enough.
How's the sack? Hanging low always or tight? Are your testicles hard or soft?
How are your pregnenolone levels? A sign of insufficient LH could be a big drop in pregenelone (since it is required when converting preg from cholesterol). This would likely create a drop in cortisol, which would also cause problems with thyroid metabolism (T3 needs cortisol to get into cells). I noticed you had a thyroid thread as well... perhaps this is why you don't feel a benefit from thyroid meds.
What is your average body temperature?
This is one of the many reasons why TRT isn't necessarily a "god send" like a lot of people think. So much more management is involved after even 1 year of TRT. I don't recommend it unless you HAVE to be on it.