HELP!!!!!!

I am unashamedly asking for some help in this post, simply because I'm vastly interested in all of you fine people's opinions. In my social psychology class, we've somehow gotten onto the topic of suicide and sin. There are a few members of my class that staunchly believe that suicide is an unforgivable sin, and that you will get sent to hell for committing it. I've never held that opinion-I thought that the only unpardonable sin was the sin of omission, in other words, not asking God to enter your heart. But they say that it's unforgivable because you can't ask for forgiveness when you're dead, and that killing yourself is murder. I believe that the blood of Jesus covers all our sins-but does asking for the forgiveness of the sin make the difference? As you can tell, I'm really confused. I'd really appreciate y'all's thoughts on this. Thanks, and blessings!