I do wonder if you could try another medication to treat the add instead of the Focalin. What about something like Strattera? This med might be less likely to cause anxiety. Another way to go, would be to try a mood stabilizer to counter any mania inducing effects of the add medication. Is there any bipolar illness in your family or that of the father's? Often this is a red flag to consider when prescribing. I would also consider family counseling. Divorce is very tough on children and this might be contributing to his grief/anxiety. One more thing...there are some good books on divorce at the library. Many will address the best ways for you and your ex to approach your child and to best handle visitation as to not cause your child undue stress. It might be best to check out a few and then discuss your findings with the father. Hopefully, he will be open to it. If not, I would go to a family therapist with your child and try to take dad with you as well.