HOW DO I STOP

MY SON IS 35 YRS OLD AND IS CURRENTLY ADDICTED TO HEROIN. HE HAS GONE FROM ALCOHOL, COCAINE AND NOW HIS DRUG OF CHOICE IS HEROIN. I ALWAYS BELIEVE THE STORIES HE TELLS ME HOPING THIS TIME THEY ARE TRUE I FEEL IF I DONT GIVE HIM WHAT HE WANTS AS FAR AS MONEY GOES HE WILL GET IT SOME OTHER ILLEGAL WAY DEEP DOWN INSIDE I KNOW I AM WRONG AND I KNOW I DO THESE THINGS TO MAKE ME FEEL BETTER I KNOW I AM LOVING MY SON TO DEATH BUT HE SEEMS TO KNOW HOW TO "WORK ME" HOW DO I STOP, HE CURRENTLY LOST HIS JOB, APARTMENT AND SOLD EVERY SINGLE THING HE AS WORKED FOR. HE WAS DOING GOOD FOR THE PAST THREE YEARS AND JUST "DABBLED" WITH ALCOHOL AND COCAINE BUT SEEM TO KEEP IT TOGETHER, HEROIN HAS GOT A HOLD OF HIM AND WONT LET GO. I HAVE SPOKEN TO PEOPLE IN ADDICTIONS AND HAVE EVEN CONVINCED HIM TO GO TO DETOX WHICH HE DID BUT HE WASNT WITHDRAWING ENOUGH TO BE ADMITTED, THAT IS THE PROBLEM HE TELLS ME HE CANT IT HURTS TO BAD TO WITHDRAWN FROM THIS DEVIL OF A DRUG.....AND WHO WANTS TO SEE THEIR KID NO MATTER HOW OLD HURTING HE HAS ME PHYSICALLY AND EMOTIONALLY ILL, DO I JUST LET HIM GO I DONT KNOW ANYMORE AND HOW DO YOU STOP THE WORRYING