B.,
I've been where you are and I know how frustrating it can be. My daughter is 3 1/2 and just potty trained two weeks ago. I've said it before and I'll say it again...I have 5 kids so I've had a bit of experience and this is what I do...nothing...that's it, that's the big advice...I don't potty train...my kids decide when and where they want to pee/poop...The boys were all just at their 3rd birthday when they put on the underwear I had purchased for them many months earlier...they all trained themselves with few to no accidents. My daughter was like your son...screaming, carrying on at the mere suggestion of trying to go on the potty. I would mention it periodically because I was getting really tired of changing her diapers. I was getting worried...thought she might go to Kindergarten in diapers! But...one Saturday I suggested she wear underwear, she said ok, I put the potty where she could find it easy and she began using it. End of story.
OK, so I guess I do some things to help the process...I buy them underwear, talk about pottying, make the suggestion, buy them a potty chair...but beyond that I don't get too involved. Now that she is doing it it is all high fives and smiles for her, which she is loving!! I just don't know what more we need to do...kids are smart, most of them get the concept, they just aren't ready...could be physical, could be emotional, could be control...whatever the reason, one moment they are not ready, the next they are. I don't think any amount of bribery or trickery on our part really makes the process go any faster.
When your son decides he wants to do it, he'll do it, and probably you won't have to deal with too many accidents since you didn't force him before he was ready.
Don't worry. This stage will be over soon and he'll be so proud of himself and you will be so relieved! I have one left in diapers, but she's only 18 months and although she acts like she wants to go on the potty, the only thing I got for allowing her to try was a floor full of poop and a baby covered in it!! No thank you, I'll wait until she's older!! We don't win any records for young potty goers, but we don't have to deal with many messes either.
I wish you well....I know how difficult this can be.
D.