sweetie, you absolutely HAVE to stay away from him. at all costs. that's the only way you can begin to heal. he is NOT WORTH another moment of your time, love or concern. he doesn't want that....he wants money or whatever else he can trade for drugs. THAT IS IT. he took advantage of your kind soul. that is not your fault.
but it IS your responsibility, NOW, to STOP. for you. for your children. you make THEM PB&J's, you make sure THEY are healthy and thriving. every time you start to worry or fret about HIM, turn your attention immediately to what YOU need, what your kids need. you hug them and let them hug you back.
you deserve so much better. you are worth the moon and the stars.