i had a 3rd degree tear with DD1, it was very uncomfortable to have sex for over a year after but it did get better, a lube called Sylk worked really well.
as for my next birth, i torn along my old epi scar and suffered another labial tear, as well as internal tearing BUT it was no where near as bad pain wise as the first time! i could actually sit down the next day unlike first time around! sex was still uncomfortable but not as much and for not as long.