These are some of the completed manhwa I've read (not every one on the list is mpreg, sadly):
• Big Apple (action/BL/supernatural)
• The keeper of the pearl (pretty sure it's omegaverse, so mpreg, It's really good, search on Google bc I didn't find it here)
• Red Candy (BL/spies/action)
• Blood Link (BL supernatural/mpreg)
• Continued Love (this one's a chinese manhua, BL interestellar & mpreg, main story finished + 2nd couple extras are ongoing), I mention it bc the MC is very similar in its passive cutesy vibes and on running away from his dominant husband lol)
• Kiss me Liar (omegaverse/mpreg, if you don't mind the drama it gets good, MC tames the dominant/promiscuous CEO and runs away lol)
I'd recommend you some CEO/mafia ones but the artists' style tend to be on a more simple side than Origin of Species and most likely aren't mpreg but pretty nice read tho:
• Trap City
• Addiction (Wolf x Fox type of thing, black and white, shorter type of manhwa)
• Yours in Blood and Soul (Supernatural BL, like 20 chaps)
I hope some catch your attention~♡(•̀o•́)ง