He’s lying to you. It could be possible if he had other developmental disorders, but he only has OCD and ADHD. He’s 16 years old, trust me, at that age they know exactly what they’re doing. His hormones are rampant right now, and he’s not controlling himself. It may be hard, but it’s absolutely possible.
What he’s doing is very illegal, and frankly, if he were an adult, this would be considered predatory behavior.
I would look into a child therapist, one that deals with kids/young adults with behavioral issues.