Tips On Relieving Constipation

I’m 35 weeks pregnant with my first child and feeling so very heavy! I still have to go to work as I don’t want to waste my maternity leave. I would rather spend it with my baby after she is born.
I’m a teacher, and some of you may know how hectic teaching can be. I feel lethargic and I drag myself to work everyday. And the heat outside is killing me!
The thing is, my doc is so stingy in giving me leave from work and I’ve been going to other doctors faking constipations and severe backpains.
Truthfully, everything is going along fine in my pregnancy that I have no excuse for any bedrest. What can I tell my doc so that she will grant me bedrest till my delivery. Please give me some ideas! Thanks!