You are underway! Just keep going now that you've started. My pet theme is don't skimp on exercise. With all the weight you have to shed, you probably can't do much at one time without running out of gas. That's ok, just be sure you are doing something. I'm a big fan of getting out the door and walking. You can start easy and gradually build up your time/distance/speed.
Why is it taking me so long to even get started? So today is the day I am starting. Step one is to write this journal and tell the universe what I am doing.
Your son sounds like a major stress generator. I have no great ideas for you, we struggled unsuccessfully with one of our 4 in a similar fashion.
He's old enough and hopefully bright enough to have some appreciation for what he's doing and what kind of problems he may be generating for himself as he moves forward, particularly if he's getting into legal trouble. Perhaps an older male family figure can talk to him. Or perhaps you can find an older teen/early 20's guy who can give him some first hand "been there/done that" experiences? If you are a church goer, explore what resources they may have available for helping him, you may be surprised what they have available.
The Buck stops here. I am responsible for my past and my future. So for today: I choose to be happy. I will seek wisdom. I will be a servant to others. I will greet this day with a forgiving spirit.