Probably nothing, though there is a chance you could cause some brain damage without ctb. Unfortunately there are no easy methods available to most people, which is why many of us have been here for years even though we want to leave this world behind. Only about 1 in 25 attempts work in general, so if you try something over the counter you may not get brain damage, though it is a risk, but you would likely get an involuntary hospitalization in a mental hospital, and in most cases people say these are pretty bad experiences, though in some more rare cases this may help some people. Ctb takes careful planning, which is the last thing a person wants to hear when they want the pain to stop asap. It may be worth it to consider sharing why you want to ctb in case people may have any ideas to lessen your pain some. I hope you can find peace somehow.