fiance cheating?

So my fiance just posted this after we got into it about the status of our relationship. Automatically gave me a nasty feeling. Would you ladies be suspicious of this? If it was about me he wouldn't have added the "you may never know" part right? We've had issues in the past with him being on tinder, he never actually did anything wrong on the app but still. And please don't tell me I'm stupid for staying with him. I know. I just want to know if anyone else would be suspicious of this? I highly doubt I'll get an honest answer if I ask him... UPDATE FOR CLARIFICATION: Yeah it was just a black picture with that caption and yes we've had issues in the past. He has commitment issues. He never gives me straight answers when it comes to his emotions so no asking would not help it would only make him shut down and refuse to tell me anything. And I don't plan on getting married if this continues. He posts about me and his on his son on Instagram so it's not about trying to appear single. I asked a friend of his to ask him about it and he said it was about old feelings for some chick he knew his freshman year of highschool.