Is this pregnancy discrimination or harassment? I usually don't stand up for myself and cannot tell you.?

I am 32 weeks pregnant and have been working with my company for about 2 years.

When I got hired, I told my supervisor that because I have a child under 4yrs old, that may daytime availability was limited and willing to work the graveyard shift. Everything was fine. She took leave for her own medical problems, when she came back, I just began announcing I had gotten pregnant.

Long story short, since she's returns from her leave, she has rode my *** for months, nit-picked at my work for minor details, and has now, cut my hours from 32 to 8 a week... shes removed me from 3rd shift because of my "screw ups" and has not made any accommodations to my daytime availability.

I am even more threatened that as my pregnancy comes to an end, I have PTS kicking in which has me paranoid, depressed and scared; and she's already hired another person to "cover me" when I am gone. I'm really panicked here.... is this discrimination (of any kind?) ? What can or should I do?