How do I get guys to quit thinking I'm joking

Taken 20/f here on OKC for a while only really looking for friends and casual sex because I'm already in a romantic relationship. I tend to be sexually attracted to inexperienced dudes and guys who are like that aren't generally too attractive at least in my area and at least in my areas OKC profiles. The problem is when I send them messages like "Hey cutie (something about their profile) (something personal) (a question) they think I'm joking? or trying to make fun of them. I tried just starting straight up as sexual and I still had one dude think i was being mean or just not reply. Is there like??? A way to go about this??