I'm on testosterone for low T. I don't feel any better and I now have "depression". Should I rule out Endo. Probs before starting antidepressants?

Discuss with your Dr. You can & probably should be on antidepressants. Simple thyroid test is certainly worthwhile because hypothyroidism is very easy to treat. You are certainly quite young to be needing testosterone replacement, however sub-optimal testicular funtion can be present at same time as thyroid hypo-function. Good luck.