Go get blood work done again and start from there. Supplements can help, but if you have a medical problem it's best to see a professional first.
Personally, 400 test is lower than I'd want it (I'm presuming the unit is ng/dl?), but it still falls in the normal range and it may have gone up since your last test. If nothing else, having blood work done will help alleviate your hypochondria.
After that, provided no new issues come to light, get yourself some and a good DAA product, like or .