This author isn't the best writer, but she makes up for it by developing long angsty plots. This story is kind of strange because it's a veela story with a twist and very long, but it involves a lot of angst and mpreg like you requested. It also eventually includes a part of the story with what happens to veela when he thinks his mate is dead. In this case, it's Draco that was pregnant, bore their child and thinks that Harry is dead. Here's the link if you are interested, and don't worry there's a happy ending.

A Mansion Built upon the Sand