So sorry about your hospitalization. It sounds like you know your own needs and boundaries, and drug addiction, or drug use, is a boundary and line. It's great he's in rehab and it's wonderful you two found one another, but he will need to stick to 100% abstinence when he gets out...

the question you have to ask yourself is are you willing to stick it through with him through this struggle? While you also need to maintain your own sobriety? Drug users most typically go back to using and have to revisit rehab several times. I've seen it happen firsthand.

You may miss him terribly, but do you think you may have a dependency issue with him? It's one thing to miss someone deeply, yet another to completely neglect one's self-care. That sounds like dependency and love addiction to me. Healthy love means you may miss someone, but you go on with your life and take care of yourself and your own needs. It sounds a bit worrisome to me on both fronts.

Try to take care of your own needs, and I encourage you to also think about the question I've posed. This could become problematic for you and may threaten your own sobriety.