Couple of ideas here:
1) Have you recently experienced a stressful or emotional event?
2) Had the flu or been sick?
3) Experienced stress over the holidays?
4) Gotten away from eating right/taking vitamins?
5) Not drinking enough water?
Any of these can really take a toll on your brain and cause you to relapse. It's scary, I know. But go back to whatever worked for you the first time. REST is key to this!