S.H.
When I was pregnant with my second child, I was working full time in a lab with all sorts of awful smells. The best way to combat this was with some Vick's Vapo Rub. I would dab a small amount under my nostrils, then all I would smell is peppermint, which happens to also be soothing on the stomach. I would suggest maybe buying a small jar and keeping it next to the diapers. Then when you go to change a diaper, just dab some under each nostril and see if it works. Good luck and congratulations!