Hi, My son is exactly the same age (3 on Apr. 27th) and I have also been having some issues with him being a little terror! =)
It's funny bec. he was such a perfect baby... until about 6 months ago! But he is awsome anyway, just strong willed. Anyway, the potty traning issue had been hard with us too. My son previously would rather go in his pants than anywhere else. Now I have him on the potty on a set scedule every day: after naps,food, playtime, and especially have been monitering when and how much he drinks. I put him on the potty 30 min. or so after he drinks. He never wanted to go on the potty, but I just have to be stern with him. I don't force him, but I tell him very clearly: FIRST potty, THEN you can go play. But you cannot play UNTIL you potty first. By stern I mean straight face, intent on this being how it is. I definately do not yell or anything, I just make it clear that these are the rules and it is important that he listens. When he extremely resists, I give him a choice of potty or back for a nap. (which sounds harsh, but he would rather ANYTHING than to go back to nap, and it works. We never had to put him for a nap, he always listened after that) I say that only when he is screaming and extremely resists the potty. Which funny enough, usually is right after he had a nap. You may choose to not do that and instead tell him that a favorite toy or movie is off limits for the day is he chooses not to sit on the potty and try. Remind him to try for only 5 min. and if he doesn't have to go he can get up. I know it might sound tough, but when you have a strong willed child like my son, sometimes they resist just to test and see what they can get away with/ and/ or they genuinely are reluctant to put the effort in. After all, it's not exactly fun. Picking up a potty book that illustrates a child using the potty might help too. My son now with our method will sit 90% of the time and goes sucessfully without any resistance at all. I had to remind him of the rules for about a week or two, but then he got used to the new scedule. I just have to still remind him when to sit. We are working on him knowing when to go himself. I hope I was a little helpful to you =)