Rule of thumb: If you're really not gay, and don't want people to think you're gay, then simply stop making homophobic jokes!
Your "joke" was essentially transphobic and homophobic at its core, and not even funny because it doesn't even make any sense, even if you accept all the built-in underlying assumptions (which themselves are quite transphobic and homophobic).
Using the word "gay" doesn't automatically make everything funny, unless you're a homophobe or a 12-year-old. If you really think you made a funny joke that somehow makes sense, then can you explain why it's funny, and which underlying assumptions it depends on? (Please don't. I'm just joking. It isn't funny, and you can't make it funny by trying to explain it.)
Homophobic? Maybe You’re Gay: http://www.nytimes.com/2012/04/29/opinion/sunday/homophobic-...
Homophobic Men Most Aroused by Gay Male Porn: https://www.psychologytoday.com/blog/the-big-questions/20110...
A New Study Reveals that Insecure Men Use Sexist and Homophobic Jokes to Appear More Manly: https://hornetapp.com/stories/study-sexist-homophobic-jokes/
Armoured Closet Gay: http://tvtropes.org/pmwiki/pmwiki.php/Main/ArmouredClosetGay
"When I grew up, being gay, being a sissy or anything like that was verboten. I disliked myself intensely and feared this part of myself intensely and had to hide it and became "Perfect Richard, All-American Boy" as a place to hide." — Richard Chamberlain
AKA The Law of Inverse Homosexuality: The more vocally opposed a person is to homosexuality, the more likely they are to be gay themself and closeted about it.
He's the strongest, toughest, manliest man in the sports team. He might hate gays and be vocal, or even violent about it. He will remind everybody that he is completely, 100% straight. That is, during the daytime. When night falls, you can find him Where Everybody Knows Your Flame with the Club Kids and Gym Bunnies. He might be browsing Grindr with a headless torso pic. He's the self-loathing gay guy who hides behind a macho façade.
http://tvtropes.org/pmwiki/pmwiki.php/Main/TransEqualsGay
The misconception that being Transgender is merely taking homosexuality one step further.
In Real Life, homosexuality and being transgender are entirely separate concepts, as they relate to two different things. Being gay or lesbian relates to sexual and romantic attraction, and means being attracted to others of the same sex. Being trans relates to gender identity, and means self-identifying as a gender different from your body's physical sexnote . This can be expressed as being "a woman trapped in a man's body" or vice versa. However, this distinction is all too often overlooked by both straight and gay cisgendernote writers wanting to insert a little diversity into their stories.
http://tvtropes.org/pmwiki/pmwiki.php/Main/CategorismAsAPhob...
http://tvtropes.org/pmwiki/pmwiki.php/Main/SuspiciouslySpeci...
Anti-gay US lawmaker resigns after being 'caught having sex with man in his office': https://tribune.com.pk/story/1561269/3-anti-gay-us-lawmaker-...
TRUMP CAMPAIGN COORDINATOR AND 'FAMILY VALUES' REPUBLICAN PLEADS GUILTY TO CHILD SEX TRAFFICKING, FACES LIFE IN PRISON: http://www.newsweek.com/republican-sex-trafficking-child-tru...
16 Anti-Gay Activists Who Were Caught Being Gay: https://www.ranker.com/list/top-10-anti-gay-activists-caught...