I'm going through a very stressful time now, work overnights & have a hardtime sleeping. I have epilepsy, been seizure free for 8 years now & I'm taking keppra (levetiracetam) & topamax can I take 5-htp to help?

Sleep. It is always best to start managing trouble sleeping without medication, such as by entertaining yourself to fall asleep, adjusting sleep hygiene (no exercise/fluids/food within 2 hrs of sleep; no caffeine in pm, regular schedule 7 days/week). If trying a sleep med, especially with epilepsy, i recommend using prescription meds due to our knowledge of their ingredients compared to otc supplements.
Insomnia! 5-htp or melatonin might help, unless otherwise recommended by your doctor. Also, sleep hygiene is worth try.