Many conditions feature obsessive patterns of thought surrounding death and existentialism. Depending on the sorts of difficulties you have, thinking about suicide can also be a way of comforting yourself during more distressing moments. I don't know whether you already seek professional help but obviously i would encourage you to do so - especially if the depression worsens and your functioning is affected markedly.

For now maybe it's best to try and stay mindful of the fact that there's rather a big difference between reading up how many pills you need to take and actually performing such an act. That is not to undermine you, more of an encouragement to take responsibility where you can and resist being excessively worried for the moment. All the best.