Just need some advice on this whole suicide thing

I will make my “story” as short as possible on “why”. I really need some ideas on “how”.  So any input is much appreciated.

I am 36 yr/o and have had severe depression for as long as I remember. Crazy violent drug addict bipolar mother and a loving yet very absent father.  Had my first embarrassing break-down ( mania) at 17 and lived a life of quiet desperation, where I latched on to a girlfriend and sucked them dry of their life-force b/c of my severe co-dependency.  Oh and did I mention that my father was a sex addict, my mother hated men ( very vocal about this) and to top things off, I was extremely anxious about sex, had zilch sex drive and ED which was humiliating as well.  But, Somehow managed to make it through a tough grad school but could never stay euthymic enough to hold down a job for very long.  My family basically supporteed me and I delved into researching every aspect of depression/ bipolar I could and tried every medication available. Luckily I can say I have tried everything b/c I had a very understanding uncle who was a doctor and if I brought him a little reasearch he would prescribe me any drug that looked like it may have an even slight chance of alleviating my suffering.  The only thing that helped was attention and sex from random women. Which was a real slap in the face to the women wwho helped prop me up in times of need, so I basically became a serial liar. I felt  needed both to survive ( a stable person who loved me as well as the quick burts of excitement from cheating).  Well, I finally thought I had met the girl of my dreams who would “fix” me and got engaged.  Well it didn;t take long to fall into the same patterns.  Still unable to hold down a job and living with someone who hated me sucked but of course she found out about the cheating and rightfully cut all contact off from me. Which of course I do not blame her for at all.  I tried even more anti-depressants , even tried ECT and lost a lot of memories and IQ. ( The only thing I had going for me was I was smart and had a great memory and pretty good looking) .  Now all that is gone.  No hope … for a long long time.  Tried it all , gave it all I had.  I want to die.  ( PS- this shit where people say that people that commit suicide are “cowards” are way off, it is the scariest thing in the world, goes against all survival instincts) .

I have thought about it long and hard here are my list of choices in order of preference:

1. Heroin or narcotice overdose – shooting them up.   ( unfortunately I am not connected to people who can get these kind of drugs for me) – so its out

2. Suicide hood with helium / and or carbon monoxide from charcoal grill – I have no idea if this is painful or not, but thinking about it is scary and also seems like a large possibility of screwing up and becoming a vegetable , which would be even worse.

3. Shotgun to the heart – using slugs or buck shot.  For some reason I would prefer this to a head shot. This would have a high % chance of working but very bloody for the finder and also the traumatic nature of it makes it something hard to do for some reason.

Does anyone have any thoughts or insights about these considering what I said of liklihood of success ( most important factor – being a veg is not an option) vs. “hardness to actually go through with”.  Or any other ideas for that matter?  Thanks in advance.

JJ