I might be partly behind information concerning CF semen and sperm motility. The female CFer can contribute a less conducive environment for conception with pretty much the same problems involving fluids. Take heart, if CFer's were all infertile, I wouldn't be here. My father had CF, three children and a shorter (48) but wonderful life.
When I posted on CFers semem, I was recalling my tests done around age 30. After being told my sperm showed low motility, I repeated the test in my lab and found the problem was in the fluid viscosity. This sounds unusual but I am a scientist I own my lab. Simple observation of other semen being dropped off at the doctor's office showed that I had less and much more viscous semen. Under a microscope, I diluted the semen with isotonic saline until the sperm motility was nearly normal. I compared the diluted semen and found characteristics like viscosity and salinity to be "normal". The sperm count was diluted by ababout 14%. The total count didn't change obviously, but the sperm density within the fluid had been reduced because of added fluid.
What I am clarifying is the sperm were fine, the swimming fluid was thick. Ergo if you haven't resorted to medical intervention yet, thin some well timed semen. This doesn't require a hot tub or rubber sheets although I wouldn't rule out a turkey baster. Seriously , placing a few (1-3) tablespoons of sterile 0.9% saline solution where the semen soon will be can't harm and might help. Better yet see a professional if just to learn your options and how best to have a baby together. For sure this problem has been solved before.
LL