Objectively speaking, the worse form of life on this planet, is the human being... I like Hinduism overall, but it has stupidities like any other religion, in order to make it more popular and reachable. People perceive themselves as the cherry on the cake, so of course, being human is the best thing you can promise them... Really? Look at your pets. Most pets have much better lives then their owners. We even kill them to prevent their suffering, which is rarely done for humans... Even the wild animals, at least have their relative freedom (we are total slaves to the society) and suffer mostly only physical pain (while we suffer both physically and mentally).
So, IMO, the worse thing that can happen, is to be incarnated again as a human. And well, you are already on that boat.. This is really something concerning, but I have no reasons to believe that the cause would be how you died, but other factors - like regrets, guilt, desires, etc., which are mostly subjective. If you don't want to be punished, you must first stop punishing yourself.
I you believe in the reincarnation, there are actually much more important aspects that you must follow. It's important what state of mind you die with, not how you died biologically. The problem with suicide is that it's commonly an act of desperation, guilt, which is not a right state of mind. Dying of natural cause is not much better either, so it's a generally a complex topic how to die "properly", so you have a better chance facing whatever is out there after you die.