A number of members - a large number, IMO - have been cheated on while pregnant, and I'm share one will be along soon to share their experience.
I just want to add that you can survive this and thrive, with or without your H, as n.e.area says.
I, too, urge you to focus on your own healing and on taking care of yourself, both for you and for your baby. No drugs, alas, lots of water, exercise, healthy food and sleep, if you can.
You're probably filled with anger, grief, and fear. You can survive. Find a good IC if that makes sense to you.
You'll probably feel some shame, too - just remember (again, as n.e.area says) that your H cheated because of his own issues, not because of anything you did or didn't do.
Have faith in yourself - you can most definitely survive and thrive.
If you like to read, here are some threads you may find useful:
http://www.survivinginfidelity.com/healing_library/reconciliation/what-every-wayward-spouse-needs-to-know.asp - if this resonates with you, I suggest printing it off and giving the printout to your H as 'something you found on the web.' My reco: DO NOT tell your H about SI until you're sure he's on board for R.
http://www.survivinginfidelity.com/forums.asp?tid=361740&HL=14993 - serjr threads for newbies
Tactical Primer:
http://www.survivinginfidelity.com/forums.asp?tid=235051
Boundaries and Consequences 101:
http://www.survivinginfidelity.com/forums.asp?tid=385631
Setting Healthy Boundaries:
http://www.survivinginfidelity.com/forums.asp?tid=231851
Before You Say Reconcile:
http://www.survivinginfidelity.com/forums.asp?tid=406548
The Simplified 180:
https://www.survivinginfidelity.com/forums.asp?tid=598080
20/20 Hindsight: What I Wish I'd Done:
http://www.survivinginfidelity.com/forums.asp?tid=161389
[This message edited by sisoon at 11:10 AM, January 18th (Friday)]