Be certain to drink plenty of water during use and take a day or two off when things get fuzzy. Dehydration may be what you are experiencing. And I'm sure the other comments people make will be helpful in finding what works for you.
I improved my fuzzy head with an occasional GABA supplement, but had to switch to 5-HTP because the Gamma-aminobutyric acid started keeping me up at night. So, I only take the GABA occasionally during the day now and 5-HTP at night when needed.