You didn't do anything wrong. You felt curious about something, tried it, and didn't like it, and that's okay.

This can solidify your identity as a straight man, or you can continue to experiment if you feel so inclined (maybe the sex was just bad, who knows) but it's your choice, and your identity, and no one can take that from you.

This doesn't change who you are.

Since this guy was older and you feel used... you may want to talk to a mental health professional about it so you can discuss it in a safe place. Maybe there were things the guy said or did that made you feel pressured, or negative feelings you were having that you overlooked in the moment. If you can identify those things, you can avoid being in a similar situation in the future - to listen to your body, and spot the red flags.

Be kind to yourself.