can't get this out of my head

I'm prolly over thinking again,and I pray to God I am,but I'm worried. I recently discovered that Rob has been using drugs and using since he was 12,so this has been going on for  a long time. I know he's trying his damndest to stop,and he's having side effects from it. Last night, he kept sleeping thru most of my visit and shivering. He shivered on and off again. When he walked me out to my car last night, he was shivering VIOLENTLY! He really had me worried,and he told me text him when I got home like he always does. He wants to know I made it home safe,but he never replied back. I just texted him again this morning and still nothing. I know a lot of the time his phone doesn't get text messages or anything,but it's not like him to not to reply back to me after letting him know I made it home ok. and now my imagination is kicking in over big time,and I fear for him. I'm afraid I lost him,and I keep PRAYING I didn't; that he's ok,and now I can't stop crying. I keep telling myself I'm gonna see him at work today,and I hope I do. I should call him,but I can't yet. I don't want him 2 hear me crying or KNOW I'm crying. I'm so scared something happened to him,and I'm praying like crazy that this isn't actual gut feeling I'm having but a paranoid feeling I'm getting due to me always assuming the worst. =( He's the best thing to happen to me,and I don't wanna lose him.