Gender is not a social construct, but the things attributed to each gender are.
You are a man in your country, but tell that to the people of an african tribe and you will get laughed out of the continent for lacking cattle and multiple wives. You would be male but not a man there.

If you have a penis, you're a guy.
If you have a vagina, you're a girl.

You don't feel comfortable? Fine, do whatever you want. Get your genitals swapped out, implants, whatever. But remember that it was nature that gave you ovaries or whatever. There is no social construct or "wrong gender". You simply get what nature gives you and it really just comes down to adaptability.