Confusing Issues with 5 HTP?

I started taking 5 HTP (50 mg once or twice a day) for depression and anxiety about a month ago. I noticed very quickly (within a week) that my symptoms were greatly improving. I continued to take it for a while (about 3 or 4 weeks) with lots of improvement in my condition. However, about a week ago, the substance started causing the opposite effect. Each time I took it, I would get instant anxiety, so I have been off of it about a half a week (I still have anxiety but it's a bit less than when I was taking it in the last week or so). Has anyone experienced anything like this and/or have any idea why this might be happening?