The reason that pregnancy can be so frustrating is because you are basically out of control. Being preggo means you don't have control over your body OR your emotions. You are no longer in the driver seat of your destiny, and are helpless to the whim of the little thing inside you. It's a painful learning experience.
Everything changes somehow...from how you shower, to how you eat, to how you clean the house.
If I just sit and study or work in the library my day goes by pretty well because that requires no real movement (except for the back and forth to get French Cocoa coffee out of a machine...YUM).
But if, like today, I spend part of it getting errands done, my evening is spent limping and waddling around the apartment with icky hip pains. Today was especially surprising because all I did in terms of errands was take some clothes over to an alteration shop (maternity pants are way too long for a shortie like moi and Seattle weather means wet pant cuffs if they are even a cm longer than the shoes!) and also spent about 30 minutes in Payless shoes browsing for stuff to wear to our Cancun vacation next week (of course didn't find anything for that particular purpose but still managed to purchase some shoes).
Pregnancy is in a way, hijacking/taking over the body. No one warns you of all the trouble you go through...pregnant women in the media etc are shown glowing and all happy with their round bellies...but no one mentions the heartburn, the worries about every ache in the abdomen, the lower back pains, the worries about being a good mother...the changing relationship with your husband.