Im pregnant and my job is trying to force to to take a LOA

I just found out Im pregnant. Per my company handbook I am required to tell my management ASAP due to the physical lbaor I do. (Im an EMT) So I did. I was told I had 7 days to get medical clearance from a doc to be able to continue to work . I have called everywhere and noone can see me until the end of Jan 2011. When I informed my HR of this I was told that I needed to take a LOA. But per my co handbook since Im NOT a full time employee( I was hired as full time about a year ago but 2 months ago my hours were cut due to business being slow) and Im pregnant Im not eligible for a LOA. What can my company due? I offered to do other positions at my company that I am completley qualified to due ( they have put other pregnant women in these positions due to their pregnacy)but was told those positions are no longer available!? Im lost Help me PLEASE!