J.M.
You are confusing him! Everything was normal until I read your 2nd to last sentence: even when he's wearing a pamper. If your are going to potty train him, do it. Potty training does not involve a diaper (pamper). It involves you, your child, a pair of underwear and a potty. Putting him in a diaper for nap, bedtime, whenever it is more convenient, etc. is only confusing him. If you really want to potty train, that means training him to go in the potty, EVERYTIME. You have to be CONSISTENT.
Each time you take him to the potty:
1. Remove his pants, sit him down and say to him "it's time to go pee-pee" (or poo-poo which takes alot more effort). This will teach him the correct word which he will correlate with and eventually say when he feels the urge. Don't say the words until he is seated on the potty. If he hears the word in route to the bathroom, he may let it go then.
2. Let him know you will stay there for as long as it takes. Take a book or game or your even a cookbook to plan dinner. (I sat in the floor for 45 minutes, playing with my iphone the first time). If you let him up because he (or you) gets bored, he will not learn to get his business done and consequently, he'll go in his pants as soon as he gets up.
3. Praise him. We sing a pee-pee song: Grant went pee-pee in the potty, Grant went pee-pee in the potty, Grant went pee-pee in the potty, Yeah, Yeah, Yeah, Yeah, Yeah! He dances., I sing, and we both clap our hands.
4. Take him back in an hour and do it all over. The time will get shorter each time until he has it down.
Just as we, as adults, forget and /or put off going to the bathroom, so do children. The difference is, our bladders are mature and we can control them. A child cannot. This is why it is very important for you to keep up with when he went last. Children have a very short attention span and become distracted easily. When they are involved in something, they are not thinking about going potty. After a while, they will begin to learn what their body is telling them and they will go on their own. It is important that you don't scold them for accidents. We call them "accidents" because they are not "on purposes". He does not wet his pants because "he wants to". It is an accident because he is busy doing what he's supposed to be doing: being a child and exploring and learning. Be patient and chalk it up to a good 3 days at home. By the way, my children were potty trained before the age of 2. I have a 3yo girl, and boy/girl twins that will be 2 in September. If you need advice on the nightime thing, message me and I can give you some pointers there, too.