Should I "hook" up with my ex husband?

We have been seperated for 5 years. We seperated because he was crazy..litterally. Since then he has spent a year in a mental health facility, and is now on the proper medication. I saw him 2 weeks ago and he has changed completely. We have been on the phone constantly since then. He is the same guy I fell in love with.....I can't help but be weary...what should I do????????? Please help!!!!