I am taking klonopin (clonazepam) 1mg and sertraline 50mg every night for depression since 1 month. Why do I keep getting very strong suicidal thoughts all the time?

See doctor NOW. Since you've just begun the sertraline, it has not yet had time to help your depression; dose is low too. Were you suicidal at times before this medication? Klonopin (clonazepam) may increase feelings of depression also. In some people, ssri's may intensify, rather than ameliorate, suicidal urges. Your physician knows how you were before zoloft -- and s/he needs to know how you're feeling now! Don't wait.