How long does it take for my OCD meds to exit my system?

I have OCD and my doctor wanted to try a new medication which took a reverse effect. Instead of quelling my OCD, it made it worse. I have gotten side effects before like nausea, dizziness, fatigue, etc... but nothing like this. Has something like this ever happened to you? If so, how long did it take for you to go back to how you were before taking the new medication? The med I was taking was called Namenda. I started with the minimum of 5 mg for a week to ten days and then for a little less than 2 weeks was taking 10 mg. I have been off the meds for 3 days now and am starting to see things starting to get better but nothing like I was 3 weeks ago prior to starting this new med. If you know about this kind of stuff or maybe went through or are going through a similar experience, if you could tell me about it, I would be grateful. Thanks ahead of time!