I think suicide is a right that someone has. But it can never be made on whim, that would be problematic. One should be in charge of one's full faculties, be of a certain maturity and should probably go through a long period of selfreflection. It's your own choice. Yes, you always should think of those who you leave behind. And yes, you should be absolutely certain that it is what you want; there are (most likely) no take-backs.
It is probably the most important decision of your life. So think it over, and I would advise against it.
It is not impossible that there is an afterlife, there is just no proof pointing towards one. That is about as sure as it will get. Think about it being as sure as there not being unicorns. Not a 100%. Just no proof.
But you'll be dead for such a long period already. You've not existed for billions of years and you'll continue to not exist for billions of years until perhaps time and space stop existing, if such a thing is possible.
With this in mind, its your choice ultimately. But with the chance for 99.9999999...% of the time of the universe's existence being spent in non-existance, this 0.0000...00001% is all the chance you get to make it something worthwhile. With all that time being spent in non-existence, is it not better to try to see if you can' turn it around? To try 'till the last breath of your natural life to get to see what beauty others witness in this existence? To get to know new people who teach you new things and broaden your horizon?
It's your choice. But I personally hope you don't do it and learn to enjoy the one thing so many that could have existed have never gotten.