Is it normal most people expect me to have a girlfriend?

I've had to deal with this too many times. People assume I am homosexual because I don't center my life around chasing women like some self-disrespecting idiot.

Misery loves company, it is said. Why should you be exempt from all the pain, heartache and wonders of love?
It's your life and you should live it as you please, not by the rules your friends(?) think you should.

Tell them to fuck off.

This not only feels like an expectation, but a requirement from my mother, aunts, uncles, and my best friend. Before jumping into a relationship, oneself must make sure they're emotionally stable and take care of themselves before caring for a significant other. I'm not a homosexual, but I don't frolic with women. People have said I look confident and attractive; therefore it begs the question: Do you have a girlfriend? To simply put it, no. There's plenty of issues I have to deal with before I get around to that.

"...especially at my age?"

You didn't disclose it.

It's none of their business.

It's very common, yes. I feel those social pressures too. It really pisses me off sometimes. I'm generally content. Sure I get lonely from time to time, but people act like I've never had a relationship before, which isn't true. Damn societal expectations...

Age, attractiveness, and confidence/personality give off vibes that you're in a relationship. Older people will look at you and think you have a girlfriend because you're young. Girls will see an attractive guy and think he MUST have a girlfriend. If you're exuding confidence, in general that just says you're happy with yourself, making people assume you aren't lacking anything in your life.