I worry about leakage
If you use intermittent catheterisation just before having sex, you should not need to worry. If you still have concerns, try wearing a condom.
I sometimes get an erection when I catheterise
Sometimes catheterisation stimulates an erection. When you stimulate a reflex erection, you probably want to use that erection for intercourse. If you take the catheter out, and let the erection go away, it will for most men be harder to stimulate a second reflex erection. Try to do a little foreplay, then catheterise and then quickly after do some more foreplay using the erection that comes from the catheterisation.
