Oh boy does your problem sound familiar, now that you mentioned the details. Maya would pee on my side of the bed and on the couch where I sat. Why....because after being home with her for 5 months I went back to work and was gone till late every evening. My husband was home but her issue was with me. It took several months to remedy. I used the Feliway spray (yes it's expensive) but I didn't know they had a diffuser. Also she was on anti-anxiety medication for a few weeks. I stopped that because it made her too dopey. ( not her high energy personality at all) I also made a point of getting home by 7 p.m. and spending lots of quality time with her . This could be similar to your kitty's problem. He's feeling seperation anxiety because he's strongly bonded to you.
He's a young one yet as is mine. He'll mature and outgrow this behaviour too. Cats are good at telling you that you are becoming a workaholic!!!!!