You see that is what is called as clouding of objectivity , and this is another feature of depression where in person feels extremely low , self critical and has lots of negative thoughts such as predicitng one's own fate before hand .
You need to realize one thing that , it is never too late to start new things in life , do not think of the future as no one can predict what is in store for each one of us , just try to correct your present by learning from past mistakes , so that you do not commit them again , and this will make everything fall into place . This is te time to realize your limitations and as well as things in which you are good at , then try to work on your limitations and exploit your potential and good points to the maximum , and you will see that you will gain a lot success and happiness in life .
So, just do not belittle yourself ,as you must be having some qualities which are appreciable , so what you need to do is to find out those qualities and just exploit them for your benefit . Always remember , when one door closes , there is always another door that opens , meaning that everyone gets lots of opportunties in life , it is upto us to notice them and use them to our benefit .
I hope this helps..So, as of now , just stop thinking about suicide , and seek counseling as soon as possible , and also start introspecting , and try to learn through it , the good and positive points which are there in you , which you can expoit , and become a success in future .
I wish you all the best... God bless..