A lot of times, with SSRI antidepressants, you feel a little bit worse before you feel better. Some common initial side effects include an increase
(feeling jittery, as though you drank a lot of coffee), some nausea, headaches, sleep disturbances (either feeling drowsy, or having insomnia). Not everyone will have side effects, and they will typically start to improve by the 2nd week of treatment.
If the side effects are bothersome, speak to your doctor.