I'm just curious as to why Erin is still not pregnant? Thry don't have protection at this ...

I mean I keep hoping she does get pregnant, but it's also about timing and such. Even with both at peak fertility and trying every month around her ovulation there's still chances pregnancy won't happen. PLUS, especially in mangas, manhwas, manhuas, etc... Pregnancy is usually used for plot so that could be why it hasn't happened yet.