Thank you for your response,
The most obvious (to me) rituals are checking doors, taps, the hob & lights before bed which I don't get involved in but I also don't encourage to stop - is this the right thing to do?
The area that I fell into was reassuring about his body. He is an avid gym go-er and is very into his fitness. What started as a question every few weeks of, how 'do I look', 'am I getting bigger', 'am I getting smaller' etc... now happens every day multiple times & we can spend hours on the topic. I didn't see this as OCD before because it wasn't a physical check but from reading up it's more of a mental check. I've always reassured him & answered his questions thinking maybe it was body dysmorphia but now it seems to be OCD, I think?
He also says that he finds himself checking whether he is thinking about having thoughts & that then causes him to panic that he wont be able to control his thoughts. The thoughts don't appear to be anything in particular but the fear tends to come from not being able to control the thoughts.