Aww, I'm sorry! I had to go through this with Aiden as well. I admittedly didn't completely read all of Jacilynda's post but I sort of did the same thing in downplaying it.
When he would start crying I would give him a hug but then just say things like "Mommy's going to work now, I'll be back later today! Bye!!!!" and I'd wave bye to him. He doesn't understand it means to go to work or what later is, but the point was that I kept my tone of voice in the same manner I usually do as opposed to frustrated or upset or whatever. And I did this for whatever I was doing. If I wanted to take a shower I did, if I needed to go into another room without him I did. I just told him what I was doing and did it. Even if he continued to cry I wouldn't change my approach until I was done.
I know it's hard to find that balance between establishing the idea that you can't cater to him 24/7 but still retain that parent/child trust of being there for your child when it's needed. It's hard but hang in there! Eventually they will learn that you are coming back. It does take some time, but it does happen!