Five weeks is not very long. Is he working on recovery now that he is out of rehab? Rehab is not a magic fix. Addicts have to continue to work on their recovery if they are going to stay clean.
I had a lot of issues of trust with my RABF. He had told me so many lies, and I didn't know what was the truth. It took time--where he was honest and open with me--before I was able to trust him again. He has now been clean for over 2+ years. He still continued to lie for awhile. I guess it was out of habit. Addicts lie, that is part of the illness.
How did I get where I could trust him? It took a long time of him repeatedly being honest to me and other people.