Authentication Error (nodejs, mongodb, jwt)

Question

I have this code for the login, and it doesn't authenticate the user, it gives me back the error response I wrote. I tried changing it so the user would stop giving back "null", but nothing is functioning. This is the code:

router.post("/login", async (req, res) => {
  try {
    const user = await User.findOne({ username: req.body.username
    });
    !user && res.status(401).json("Wrong Credentials");

    const hashedPassword = CryptoJS.AES.decrypt(
      user.password,
      process.env.PASS_SEC
    );
    const OriginalPassword = hashedPassword.toString(CryptoJS.enc.Utf8);
    OriginalPassword !== req.body.password &&
      res.status(401).json("Wrong Password!");

    const accessToken = jwt.sign({
      id: user._id,
      isAdmin: user.isAdmin,
    }, process.env.JWT_SEC,
        {expiresIn:"3d"}
    );

    const { password, ...others } = user._doc;

    res.status(200).json(...others, accessToken);
  } catch (err) {
    res.status(500).json(err);
  }
});

what it gives back is the "Wrong Credentials" string I put; I console logged the req.body.username and it gives me back my username, but the const user just keeps giving back null. I hope I can find some answer, I'm losing hope already