When to slow down?

LINDA • I'm a Bronx native, residing in Washington Heights. I'm 32 and a first time mom! I'm a Union Carpenter 4yrs.
I'm a first time mom with no symptoms or movement from my baby. I'm 20 weeks today and have always been frightened of child birth but so far it's a breaze! I'm a Carpenter working out in the hot sun all day building the city. I then head to school after work twice a week for 4hrs. On the weekends I'm running errands, cleaning, gym,
 or with my niece and God daughter out on the town. I feel fine but everyone else keep saying should you be working? Or how are you going to finish school? I'm amazed that people actually think women are incapable of multi tasking while pregnant! I have been questioning myself when is the best time to slow down?