DS scared of peeing

Maryland08

3 days ago DS (17 months) saw himself pee in the tub, we didn't scold him or say anything. He screamed and was shaking and crying hysterically. We comforted him, drained the tub and started over. He peed 2 more times that night and we repeated the draining and he repeated the uncontrollable crying . He did the same thing the past two nights. We tried cheering when he did it to get him to laugh but nothing works. I am at a loss of what to do! Now he is scared to even get in the tub. Tonight we let him roam around the bathroom in his diaper to get him to pee before he got in the tub. He did, but still went in the tub and still the non-stop tears.

We haven't even come close to starting potty training and he doesn't even acknowledge that he has done anything in his diaper.

Is this normal? I know all babies are different but I have never heard of this, nothing is even showing up in Google!