I have a species of intelligent human-like creatures. One of the things that makes them different from humans is that unprotected sex has a very high likelihood of resulting in the female becoming pregnant (about 80-90% chance, barring genetic or illness-related hindrances to fertility/virility). They also have a much shorter gestation period than humans, though birth is almost equally as painful.
The high rate of pregnancies is due to a quirk of their reproductive systems, wherein a female typically ovulates after experiencing orgasm instead of having a fertility cycle. Children grow at roughly the same rate as human children. They're also a K-selected species, meaning they put a lot of resources into raising a small number of offspring, rather than having a lot at once and leaving them to fend for themselves.
Because of the high-risk of pregnancy, their society starts giving sex-education to youth from a fairly young age in order to reduce teen pregnancies and the inevitable increase in death-from-childbirth that would cause (their tech is roughly around late medieval levels, just with better hygiene, so not a lot of options to reduce that overall). I am curious how such a difference in reproductive success would actually affect the species on a biological level, though.
Humans commonly have sex for pleasure because there is a (relatively) low chance of women getting pregnant from it.
Basically, with such a high chance of a female becoming pregnant after intercourse, would my species actually have a libido on the level of humans, or would it work differently? Would there be any desire on a biological level for casual sex (sex for pleasure or to deepen bonds rather than to have children), particularly in teens going through puberty?
Edit: Ignoring the potential use of contraceptives and abortifacients, since I'm asking on a pure biological level "how often would an intelligent K-strategist species with a high success rate in reproductive attempts experience the desire/urge for sexual intercourse?"