I dont want to lose my family!?

Hi; I am 17 years old and my ex-girlfriend is 19 and we have a 10 month old baby and we were living together until a week ago. We had been having problems for the past months because of the people i work with because i started going out and doing stupid stuff like smoking weed like twice a week and did cocaine once i know it doesn't matter how many times i did it because regardless it was wrong and irresponsible of me, also we had been having problems at home because of our attitude with each other and me being selfish by sleeping until late and not helping her around the house and with the baby. Her and my son are my everything I LOVE THEM with no limits at all i would do anything for any of them two to be ok i mean they are my family and to me there is NOTHING more important than that but my decisions were showing the opposite so little by little she started losing hope in me to change because we would argue and i would say all this stuff that i was going to change and never did them or i would do them for a little bit and then be back to the old me, i am young and still maturing and growing up but i will not blame that because i should have been there with her every single night after i got off work support her love her in every way possible and the same with my son. I had been wrong and i didn't see it until a week ago when we had a fight and i had to go to my parents house and talked and she doesn't feel like she can trust me again, she says she loves me and misses me but its hard for her to trust me. We get along great we are a great team together we love each other and i know i could love her and respect her for the rest of my life and the next one if there is another one. Now i understand every single time she tried to talk to me or get mad at me or fix usand this time i really will not fail her if she gives me the opportunity i just need to make her understand and believe me that it REALLY WILL NOT HAPPEN AGAIN! EVER! i love her and my sons too i want them back i want us to one day get married and be together forever. i know i messed up before many times but i finally understood where my position should be i just need that one opportunity the real one to show them who i really am i want to make up for every single time i just need that chance i love them and miss then soooooooooooooooooooooooooo much! i am attending to college because i want to give them my everything and a beautiful life with love understanding and stability. any advise on how to make her belive me one last time ????? any advise