going back to school..but also expecting.

I've enrolled back in my High School because i need only 3 more credits to get my diploma. And seeing as im expecting a child, i want to get the 3 credits out of the way now, because i know that if i put it off any longer i wont have an intrest in doing so because of the baby.

I go to a catholic school, and the reason why i enrolled back in my catholic High School is because Semester 2 starts this coming Friday, and i thought i would have a better chance getting in there than any other school seeing as its so close to 2nd Semester.

Now Catholic High Schools are exprmely strict about being pregnant and going to school. And I found out from my best friend that they will only keep you until your 6 months prenant, and then ask you to leave or send you to a school where girls who have gotten pregnant go to, to finish up the school year.
When my bf/fiance and i heard this from my best friend, she suggested that we hide it from the school...but you can only hide a pregnancy for so long until one day POP! you've got a HUGE tummy! PLUS! there are 3 sets of stairs in my high school, and i have no problem with walking up them, but i have a feeling that when i get too big, i could possibly fall or slip down some stairs. I know that when one of my friends were pregnant and in high school, [they let her stay until she was 6 months] -but left earlier cuz she had a premature birth- they gave her a elevator key, but they knew about her pregnancy, and im not going to tell anyone or teacher about mine..so either i have to be really careful or tell them and get a key..

But how can i hide this pregnancy?? I know teachers, if not my two male teachers finding out my female teacher that i have will for sure find out or suspect something. I mean like i said, you can only hide a growing belly for so long until someone asks the question "are you pregnant?"

My high school also has uniforms because its a catholic school and majority of catholic schools wear uniforms. Now, i have maternity pants that i can wear because they are the same colour as my schools pants, the only thing i have to get now is a larger school shirt so i can wear it as i get bigger.
If anyone does find out -like teacher wise i can tell them in a few months behind what i really am. Because right when im 7 months, will be when my exams are starting and i NEED to do my exams to pass. so i could tell them im 5 months when exams start instead of 7 that way they dont kick me out and i still get to do the exams...

Anyone else been in this situation?