I have studied many of the old and new teachers (Seth, Abraham et al) for years and years and it is my absolute and convicted belief that there would be no punishment meted out to anyone because they chose to take their own life. Who is going to punish us? Who is going to decide that we should be punished for suicide?
There is no-one 'in charge', making decisions about what is right or wrong, whether we've been good or bad, and whether we should be rewarded or punished. No-one - NO-ONE - makes decisions about our lives except us. WE ARE IN CHARGE. WE GET TO CHOOSE ALL OUR EXPERIENCES!
BUT (and it's a big one
) - it's my belief that we create our own realities (through our beliefs and expectations) both here in physical AND in the 'afterlife' (which of course is also the 'beforelife').
If I really, really believe that there will be consequences for taking my own life, and I therefore feel unhappy about doing it, feel bad and guilty etc. - but do it anyway - then it doesn't take much imagination to realise that I'm going to be as unhappy afterwards as I was before. It's not punishment, or karma, or somebody making me 'pay' - it's me beating myself up in exactly the same way 'up there' as I was doing in the physical world!
You mentioned that your nan had Alzheimers: Abraham explains Alzheimers as a kind of 'one foot in physical, one foot in spirit' situation. Abraham explains that people who choose such a condition don't feel that they can leave physical yet, so they kind of go 'part time': physically still here, but mostly already back in the spirit realms. It makes sense, if you think about it.
All deaths are suicide, inasmuch as we each decide when it is 'time to return'. We chose to come here, we choose when to go. Even 'accidents' are not accidents. We were not sent here to learn lessons, like naughty schoolchildren. We have chosen to come here because it's a physical experience, because we wanted to expand the Universe with our experiences, we wanted DO PHYSICAL STUFF!
We almost certainly chose to experience things we wanted to find out more about - to learn how it would feel, to know how it would play out - and we will have factored those in to our experiences in this lifetime. BUT NO-ONE TOLD US WE HAD TO! It was entirely our choice and we made that choice happily and joyfully. I do not believe that we get 'sent back' to learn lessons we didn't learn this time round. We might CHOOSE to come back and experience something, or learn something, but it will be done because the idea gives us pleasure, not pain, and because we WANT to.
You sound to be very unhappy and very confused. Can I suggest that you do some reading (I absolutely and unreservedly recommend the books and recordings by Esther and Jerry Hicks - the book 'The Astonishing Power of Your Emotions' would be a good place to start.) You could also watch some of the Abraham videos on YouTube, or go to their website and download their introductory MP3 (which is free). I recommend them because their messages are uplifting and utterly positive, but make complete sense. I have never been able to read, listen to, or watch Esther channelling Abraham without feeling uplifted!
You can't jump from a place of feeling unhappy and confused to a place of happiness and joy in a single leap, but if I were in your shoes, I would postpone ideas of suicide for a while and spend some time finding ways to begin to feel a little bit better first. Find a coach or a mentor perhaps, someone you can talk to and discuss your fears with, who can help you to work your way through this.
The world out there is a mirror of your beliefs and ideas about yourself. It seems that you want more love, more kindness, more warmth, more happiness - and it's out there waiting for you, you just need to remember how to let it in. We can get very 'off course', and sometimes we need help to get back on track. The help is out there as well - just ask, and it will come to you. Look at the help you got here!
Another site you might find interesting is another favourite of mine, nderf.org. It is thousands of accounts of near death experiences from around the world, and there are a few that are from people who tried suicide (which obviously didn't work!) But it's a fascinating site and will confirm what I have said above: ain't no-one out there telling you off, there's just you. Start by loving yourself.