Haru wo Daiteita - Embracing Love - Vol.01 - Youka Nitta
This is a long ass Yaoi with switching, but the couple usually sticks to a younger seme/older uke dynamic.

So. Much. Drama. And angst, and shouting, and it gets a little confusing sometimes. But I read the whole freaking thing and it's entertaining to say the least. I love how much the couple loves each other.

Also! there's one page with spanking : >