How did you guys get your fur baby ready for baby?

I have a pomeranian Chihuahua. His name is Richard and i love him sooo much...lately he has become very possessive and aggressive. Ive heard that playing baby noises...washing with the baby soap and letting him get used to all the baby equipment around...it seems like its not working. Ive had him since he was 6 weeks and he will be 4 next month...i dont wanna have to leave him with my mom! 😭😭😭😭