I need work advice.

I work at a vet clinic and I'm 32 weeks. I have struggled for the past month with my job ignoring my challenges and not offering a solution. I work as a receptionist but we are an extremely busy practice and I'm just CONSTANTLY up and down and running around the clinic for clients. I truly love my job but there are days that I literally cannot walk. I have to hobble and hold onto things for support and I get so much pain from doing it but because we are so busy, it's hard for my coworkers to help me as much as I need them to. I've expressed I need to be off to the side answering phones or something instead of being in the hot seat but my manager said he wants me there because I'm the best person to be up front. So I got my Dr to write me a restrictions note to where I'm only allowed to be up and down twice an hour but it's so unrealistic and I know they won't follow it whatsoever. I only work 3 days or so a week but I dread going everytime lately because I know I'm just going to be miserable and nobody will care. My Dr told me just to let them know when i want to stop working and they'll write me off but I still have 6 to 8 weeks before I have my baby most likely and that's a long time to have free time with no money or baby. But I just absolutely dread work. My last day is the 28th but I don't think I can make it that long now. I don't know what to do. I want to go ahead and leave but it's hard.