How likely is it to get pregnant on your 'fertile' days with unprotected sex

It's very likely. But of course it depends on the woman's fertility and the man's sperm as well as other factors.

Asking about world wide probability about pregnancy is not really meaningful to one person, of course. If there's a 42.3% chance, you are either in that 42.3% or you are in the 57.7%. If you are in the 42.3% percent, you are still 100% pregnant.