I'm currently taking 20 mg of fluoxetine since mid December and during the last 2 weeks I've been feeling really sleepy and tired everyday. I used to take sertraline before and this never happened when I was taking it, I had to switch to fluoxetine cause it was making me gain a lot of weight and couldn't lose it. Isn't this side effect only suppose to happen during the first weeks of taking it and then go away? Why is it happening after months of treatment? So does that means this side effect will not go away as long as I'm on the medication?