?? about and bf????????

me and my bf watch sometimes and sometimes he wants me to masturbate him while he watches this happens like once a month ...does he do it bcs he does not desire me or is it normal ?also is it normal to watch with him or will i induce him to other women by puttin .?sometimes he will be like put some on and i do bcs im not against it but wat do u ppl think men do this?????