Bear with it....
It's probably a stage, but one that might last a long time. My son was quite a "velcro baby". It was only when he was 3 years old that I could use the toilet w/out him often pounding on the door, demanding to be let in (often I *would* take him in w/ me, but sometimes I felt like I desreved a little privacy).
One strategy that I used was to tell my son "mama has to xyz and I'll be right back (e.g. toilet, shower, etc.) and then be right back and say something like "See, I told you it was just a minute".
Some kids do better if you put them in an exersaucer or something when you need to do things like bathe.
Will he be happy if other folks hold him and play with him? That will give you some relief.
The other thing is to just realize that a little crying will not kill him and that you are a human being who deserves to be able to do things like shower by yourself and if he cries for a few minutes while you do it, so be it. Part of a kids healthy development is learning that they can be momentarilly upset, cry, and he will be OK (again, I am talking about minutes, not letting a baby wail unconsoled for hours).