I need advice...

Martha • 17years young ... NOT TTC. love you all!
My boyfriend went away for the weekend... And we have been having an interesting sex life... I mean it's great. But he always goes place and gets high or drunk without me.. And all I can do is sit here wondering if he's loyal to me. I trust him, however I have been cheated on so many times before him. Last night he asked me how I felt about marrying him. And my immediate response was yes! He wants to get a place together so we can grow up and stop being teenagers. He's 18 and I'm about to be 18... I just need to know... Well I don't know.. He said he would be home at 1:00 pm today it's 6:00 pm right now. So you know I'm just sitting at home all in my lonesome, with my 7 cats, and watching supernatural on Netflix... He wants to get married when I turn 18 and I'm okay with that.. I just don't know how I feel about him leaving me all the time to go to his friends house and get high or drunk? HELP!!!!!