If you feel you have to go into to work tomorrow,do so,
but on the way home go to the doctors and get signed off for two weeks,
your description of your day and work environment rings bells,
I suspect that if your body and mind was not having to also cope with pregnancy, you would be closer to the water off a duck's back coping strategy,
you must listen to your body, it's trying to look after you and baby,
I have had endless pregnancies, some I have worked up until the last moment, and some I have had to take real stock as to what is the highest priority at that precise moment, I don't think I have always been successful in the decision process, with much regret,
A contributing factor in my choices has been my over commitment to my work environment, and heightened sense of obligation to others,
take the two weeks, turn the phones off, have a swim, hot baths, rest, give your body a boost into doing some really important work,
don't paint, shop and other energy drainers,
If you don't feel it was really what you needed, go back,
if you suddenly find that it has really changed how you feel physically and physiologically ask the GP to continue your sick leave,
the times I did stop and really take stock and gave myself a chance to hear what my body needed, had far better outcomes than when I foolishly carried on and it went on to have long ranging effects.
I hope you feel better soon.