I don't know if it's affecting your fertility, but if you can't retract your foreskin, you should talk to your doctor about that.
It can sometimes be caused by a skin condition - https://www.nhs.uk/conditions/phimosis/
Six months isn't a long time to try, but since you are both in your 30s, there may be things you could do. You might try our Fertility forum - https://www.medhelp.org/forums/Fertility-and-Trying-to-Conceive/show/96
Definitely talk to your doctor, though. Sometimes, phimosis isn't a problem, and if your semen is getting into your wife, I don't think that would be the cause, but get it checked out, if you haven't addressed this specifically with your doctor.