Is this considered discrimination?

I'm currently 27 weeks pregnant. I started a part time job about 8 weeks ago. When I started, I would volunteer for every extra shift that I could. Someone calling in, short staffed, things of that nature, I was there picking up hours. Shortly after I started i developed severe anemia. At certain times, I get shortness of breath, blurry vision, rapid heartbeat,and feel extremely faint and nauseated. I've communicated this to management and been sent home twice because of it. I told them that if I can just have short breaks when this happens and not be on my feet the entire shift I will do just fine. The job is at a retail clothing store and the shifts are only 4 hours long so i do my best to just push through.however, Management isn't being understanding at all. One shift, I pulled my manager aside and told her I needed a 5 minute break.she allowed it but was annoyed.she sent me home as soon as I returned to the sales floor.since then, i have only been scheduled 4 hours a week and I'm very much singled out when I am there.other employee's will walk past me and tell me to pick up the pace, tell me to redo things I've done, and make sure that no matter what task I'm doing, I'm on my feet at all times. Managers will single me out in front of everyone and loundly announce when my shift is over and I can leave. They started searching my bag before I clock out for some Reason.Im feeling very much attacked and wondering if i should contact the HR department.