E.N.
Dear Elisa,
This is the sure-fire way that I got all three of my children potty-trained at an early age.
In order to go #2, he needs to relax and not think about the issue. When he was sick, he could have had a little diarrhia or constipation, which may have given him some discomfort.
In the early morning and the diaper was dry, I quickly picked my child up and told the child to wait to go potty so that I could put the child on the potty, get the chold's juice and put on the TV. If you do not use the TV, I did the same thing but instead chose one of the child's favorite books. I would sit next to the potty chair and let the child have the juice and read with the child until the child felt relaxed and the child learned that relaxation process in order to be trained. We read many a favorite book and did a lot of communicating while on the potty. Take the time, it is well worth the effort.
During the day, 30 minutes to an hour after any large meal we went to the potty for TV time or book time, dependig on the child's interest and what I wanted to introduce to the child. During the time that the child was sitting, I would ask the child if #2 was coming, and the child was able to understand that this was a fun and learning time that should not make the child anxious.
Even if we went shopping for a long period of time, the potty chair went in the van and we still had that private time in order to have this learning process to take place.
Good luck!
E.