Ok first of all, most places have a probationary time period when you take on a new job....most places is 90 days. If you can't do your job duties you can be released from your job. you are over that time frame...they can't let you go now without giving you warnings. it's against the law...and I dont' think that they would let you go on the first go round and def not because your pregnant. (depends on where you work too.)
the right way to go about this is to get a doctor's not about your working. have him list your limitations and restrictions. ie: can't push pull lift more than 20 lbs, can't bend, can't sit/stand/walk for long periods of time (10-20-30-40 mins at a time) and approch them about this. if they have a place to put you like a sedintary (sp) posistion. i have no idea what is is you do...if you already said it sorry i didn't read all the posts. A lot of jobs don't consider being tired as a disability....it's something that comes with pregnancy. sorry
Mat leave is something that you have if you qualify at your job...you need to get the policy for the company and read it and go from there. you most likely haven't bult up enought time to be off the whole 6-8 weeks. but mat leave is for PP leave. If you leave before that point you have to have your doctor involved....at this point you most likely havn't built up enough leave time.
I work in disability and i do this all day long ...if you have anymore questions let me know.