Hi,
Congrats on your pregnancy!
I rode my bike up until I was about 6 months pg and had no problems. The biggest thing was my tummy being in the way when I leaned over to reach the handle bars. I did go out and buy a gel seat for my bike which made a big difference. Also, my rides weren't that long..maybe an hour at the most. I usually rode around to do errands.
You can find some good cycling clothes for preggies at title 9 sports (www.title9sports.com)
have fun and good luck.