Celsie,

You did not have to tell him that you are pregnant, so surely by doing that he can see your honesty...
I'd simply e-mail back & said I'd love to take on this role, Thanks!

I'd be honest & ask him what the plan is from here..... Yes you are preg, but heck you can still do your job & also point out that you plan (if you do) to return to the work force after X amount of time off... (it would probably be unpaid as you'd ahve not been there 12 mths?)