I have been taking venlor xr 2 months back due to postpartum depression. Initially it worked very well. But since last week I am having sleep problems. Even if I am very sleepy I am unable to sleep. What could be the reason ? Is it that the medicine has stopped working so soon. But I have read it has worked for years together. Kindly help me out. I am suffering a lot and I have a baby 5 months old to take care of