Im so sorry you've lost your cousin and your grandma, losing anyone is hard, losing two members of your family must be dreadful, it sounds like you're being a bit to hard on yourself. Grieving for someone is a long, lengthy process, its not something that happens over night. Its really really hard, but things will get easier as time goes on and you will start to remember the happy times you had with Sam and your Grandma.
I dont mean this in a mean way, but for your girlfriend to cheat on you, especially after all the really tough things you've been going through is heartless and cruel and frankly you deserve better. I know its not as easy as just moving on from her, but you will find someone else, someone better who will treat you right.
Losing someone so young and so suddenly is a big shock, its very hard on you, and with everything else it must be really overwhelming for you. I really think you need to talk to someone about getting some help, particularly if suicide is starting to creep into your mind. Talk to your parents, do they know you self harm? If it really isnt possible for you to talk to your parents you should try to talk to your local doctor about getting some help.
Suicide is the answer to all of this, its not. It will devistate your family and everyone who knows you. Have a read of these threads
here and
here hopefully they will help you to see how wrong suicide is.
Please talk to someone, on the forums, talking to
The Supporters or by using
Live Help where you can talk to them one on one.
The Samaritans and
Childline are also available 24/7.
Please look after yourself and stay safe.
You can get through these black times, I know you can.
Aimee xx