I'm so sorry life hasn't been kind to you; no one deserves to suffer like that.
If you want to CTB, my suggestion is break the entire thing up into very tiny steps. Like today, research two different methods, and decide which of those methods sounds better to you. Tomorrow, compare the winner to a different method.
Once you've done enough comparisons and you think you've finally settled on your method, make a plan. Like, this day you'll think about the things you want to avoid (I don't want my mom to find my body, I don't want my dog to see my corpse, I don't want to be difficult to clean up), and try to think of a good place (like outside in the woods).
If you break everything up into very small steps, it's easier to make a decision, and each little step gets you closer to your plan. Then, when everything is finalized, this is a plan that took you months to make and your anxiety won't let you deviate from that plan.