How to re potty train my kitty!?!?

I have a male cat who was perfectly potty trained when i got him as a kitten. he used his litter box for about 6 months and then started squirting all over the place trying to mark the house from the outside cats. it got to the point where he squirted so much he never peed in the litter box. we got him fixed and he used his litter box again and didn't squirt anymore for about a month. then he started squirting again but not much and now he just plain pees around the house. he still goes to the litter box to poop but not to pee! can someone please help me find a way to get him to use the litter box for both pee and poop! he has never pooped outside his litter box, only pee