Hey .. yeah.. I took NAC for several months and I got an energy boost at first, then it became much less noticeable. It really did help with my anxious thoughts & OCD. I attribute it to enhanced glutathione production and glutimate-GABA balance.
Now I am doing a "methylation protocol" with help from the good folks at the Phoenix Rising forum. In a nutshell, it's taking combination of methylcobalmin B12 and methylfolate in an attempt to restart the body's natural production of glutathione and other methinone,etc.
I am having a mostly successful start with these supplements, and I have been able to discontinue taking the NAC. My mood, energy and OCD reduction remains just as good or better.
Any doctor should be able to order a test. A web search for "discount lab tests" will show you where to order some.