Effexor dosage –

I have been on Effexor for about 2 months to help with my social anxiety disorder. My doctor started me on 35.5mg a day for a week, then eventually upped to 75.5mg a day. At this point I was feeling fine. Eventually, my doctor increased the dosage to 225mg and then 300mg. Oddly enough when the dosage increased, the effect was decreased. I am also taking Risperidone (2-4 tablets) before bedtime, could this be countering the effect of the effexor?