I am always sleepy and with mild headache i suffer for tbi due to a combat injure and been taking sertraline and diazepan. why this is going on?

Drug side effects: If the diagnosis of post traumatic depression is correct it could be due to insufficient medication or conversely side effects of the drugs.

TBI or meds or both: Tbi can cause both headaches & tiredness & if not successfully treated continue as problems. Diazepam can cause tiredness if dose too much. Sertraline usually doesn't cause tiredness or headaches though possible. Follow up as soon as possible with treating physician. Repeat neurologic & psychiatric evaluations are in order.