Congratulations!
My pregnancy was also a surprise. DH and I wanted children, just not quite yet. I was about 7 weeks pregnant when I found out...thought I was late, tired, etc due to stress from my final exams...boy was I wrong!

It took me about a week to finally get a test and take it...and when it came out positive, I also laughed and cried...I was happy, in shock....every emotion out there I was feeling!
I was lucky and never had morning sickness, but I was VERY tired during the entire first trimester. Second trimester is the best...when you have the most energy and feel like a normal person...also when you start feeling the little baby move, which is just amazing.
Your doctor should give you some info regarding all of the tests they can do. I forget exactly which test tests for what...I know it includes Downs, spina bifida and some other things. We didn't get any of the "extra" tests done since we were young, low risk, and wouldn't change a thing even if our baby would have been diagnosed with one of those things. It's up to you and your DH.
I hang out on babycenter.com a lot...I've found some pretty good info there. They also have TONS of message boards, including ones for people due the same month as you...those are the best, IMO.

You can also sign up to receive emails each week which give you info about what you and your baby are doing that week. I always looked forward to those...and still do for DS!
I wouldn't change a thing. DS is the best thing to ever happen to me aside from marrying my DH.
If you ever want to chat, I'm just a PM away.
allison