It took my husband over 9 months to make the changes. His personality after 3 months was very much like it was when he was drinking, but gradually I saw a change and now he is more like a "normal" person. Once in a great while I will see a few seconds of the drinker come out, but he always catches himself and adjusts his sail and moves right back to where he is suppose to be. And, I must say I am the same way, working my program, sometimes I slide back into the old me, but I catch it and move forward.
It takes time. At three months he is just starting and has a long way to go, but he has got a good start.
Is he attending AA on a regular basis? Did he do 90 meetings in 90 days to start? If he went to treatment, is he doing the aftercare? If he is working on these things, the changes will come, gradually. It took years for them to get the way they were and I have been told it will take years of sobriety for them to get where they want to be. Be patient, it should get better.