Deficient serotonin levels?

I was reading up on the symptoms of deficient serotonin levels, and I believe I have a few of the symptoms. Such as constant fatigue, (no matter how much sleep I get each night), anxiety and an OCD-like germ-phobia. The biggest problem, however, seems to be this ever-present brain fog, I can't remember an instance in the past several years that I have been able to think clearly. Compounding this problem (or perhaps the cause of it), is my inattentiveness, for instance I am having problems staying focused writing the post. This general problem could be attributed to emotional instability, I'm not altogether sure, although I seem to get teary-eyed over minor things and I know that is definitely not normal behavior. I also have raging social anxiety. Honestly, I don't know what to think about my self anymore, I have virtually no self-esteem, I'm probably slightly paranoid, irritable. Can depression be playng a factor in all this?

Sounds alot like what i had.The brain fog included.
Check out this link to make sure you dont have this, before moving on to other reasons for these symptoms.
http://www.holistichelp.net/candida.html
If you eat alot of sugar or things with carbs its a possibility.