I’m very sorry to hear of the pain you’ve been going through. I urge you to discuss exactly what you’ve stated here with your psychologist. It is possible that you may need immediate medical attention and your psychologist can help you to get it. These resources may also be helpful:
Pastoral Solutions Institute
National Hopeline Network
Regarding your question, your story is familiar to me because, as a teenager who suffered from serious depression, I too plotted how I could kill myself and avoid hell. If it would be helpful to you, I recommend you read my story. Thankfully, I received the help I needed at the time and eventually learned how mistaken I was about my theological assumptions.
Here, I will simply tell you that I’m afraid you have seriously misunderstood the Q&As the apologists have handled on the issue of suicide. The questioners we dealt with were asking about people who had already committed suicide, not those who were plotting their own deaths. In a case where someone has already committed suicide, survivors may hope that their loved one did not fully understand what he did, that mental illness might have mitigated culpability, and that God provided him with an opportunity for repentance before death. And they certainly may pray for the repose of their loved one’s soul. But we won’t know for certain, this side of eternity, the fate of an individual who commits suicide.
In your case (and as it was for me too), you are plotting how you may defy God’s commandment against self-murder so that you may do as you wish. The essence of hell is the choice to defy God and, by such defiance, to separate ourselves from him. We may tell ourselves that “all [we] want is just to be with God” but our actions demonstrate otherwise.
I will pray for you and I ask CAF readers to keep you in prayer too. Please seek the help you need so that you may overcome your illness and your temptations to despair. God loves you and, if you will allow him to do so, will give you the grace to carry your cross with him. God bless.