I agree with the restraining order idea. If he still keeps messing with you after that simply call the police. It might take him a minute to realize but I'm sure when the law is involved he won't keep bugging you.
I'm sorry to hear you have to go through this; especially pregs. I can relate as far as stalker goes,minus the pregnancy part. Have you tried a restraining order? Not picking up your phone? Any idea as to why he acts this way? Is your bf/hubby aware of this?
My best advice is to file a restraining order. You don't need his ****. Preggers or not. Good luck hun!
Get a reatraing order sounds like u have a reason to fear for u and baby or report him for stalking and harassment and theirs a app u can download to your phone to block peoples calls too