My daughter has always wanted her diaper changed, even if it was just a tinkle, so I can't help with the crying during diaper changing, although I agree it might be because of location (i.e., on a table, afraid of falling off) or--and this is the hard one to address--something else that might be happening at daycare that he doesn't manifest his distress about until he's home with you, his parent, whom he knows he can trust and show you his anger/fear/mistrust, especially if he's too young for much verbal talk.
The bath, I can relate to.
My daughter was 2 when she suddenly hated taking baths. Up until then, she loved baths and playing in them. We couldn't for the life of us get her into the tub. Finally, I had to get into the tub with her, or she wasn't going to take a bath. Anything in the tub, she had a major fit over (lint, hair, stuff). This went on for 6 mo, maybe a year, until we gradually weaned mommy out of the tub (she grew too big for both of us to be in the tub together).
At the time, we didn't know what was wrong. However, after we discovered she has Sensory Processing Disorder (SPD), the fracas with the bathtub made more sense. We'll never know if it the water was too cold, too hot. If the open space/expansive of the bathtub scared her, or if the water depth did. When I was with her, then everything was okay. Mommy was fine, mommy wasn't scared, and my daughter had someone to "keep her safe."
SPD is just something to think about. My daughter is now 8 and, other than getting her into the bathtub (which, with our crazy schedules, it's sometimes a challenge to find an open night), we have no more screaming and tears.
A. C.