How long before sertraline (50mg) is out of your system?

Day 4 of not taking sertraline now, to be fair I forgot over the weekend but yesterday my doctor told me to stop taking it because it's having no effect whatsoever on me and just giving me side effects such as sleep problems and not eating enough.

I see some improvements, especially in my sleeping, it was ten to 8 before I woke up this morning (late for me) but I still slept this afternoon and I'm not that hungry still etc.
Does anyone know how long it takes to get out your system completely? I am very worried I'm going to go back into a depressed mood again soon, the longest I'm in a good mood for is 2 weeks (same for depression) and I've been up, as it were, for a good week now. :wacko: