Why is my app doing a request on a different port?

Question

I am building a nodejs, reactjs app and i am having issues for making requests from my reactjs part of the app to my API. I am using concurrently, so i made a proxy:

"proxy":"http://localhost:5000/"

Port 5000 is where my API is running and Port 3000 is where my ReactJs runs.

When i try to register a new user i get the following error

Cannot POST api/users

And my console shows what url is trying to request http://localhost:3000/api/users

But instead it should be http://localhost:5000/api/users

This is my Register.js:

import React, { Fragment, useState } from 'react'
import axios, { Axios } from 'axios';


const Register = () => {

    const [formData, setFormData] = useState({
        name:'',
        email: '',
        password: '',
        password2: ''
    });

    const { name, email, password, password2 } = formData;

    const onChange = e => setFormData({
        ...formData, [e.target.name]:e.target.value
    });

    const onSubmit = async e => {
        e.preventDefault();
        if(password !== password2){
            console.log('Passwords do not match')
        } else {
            const newUser = {
                name,
                email,
                password
            }

            try {
                
                const config = {
                    headers:{
                        'Content-type': 'application/json'
                    }
                }

                const body = JSON.stringify(newUser)

                const res = await axios.post('api/users', body, config);
                console.log(res.data);

            } catch (error) {
                console.error(error.response.data)
            }

        }
    }

  return (
    <Fragment>
        <section className='container'>
        <h1 className="large text-primary">Sign Up</h1>
        <p className="lead"><i className="fas fa-user"></i> Create Your Account</p>
        <form className="form" action="create-profile.html" onSubmit={e => onSubmit(e)}>
            <div className="form-group">
            <input type="text"
             placeholder="Name"
             name="name"
             value={name} 
             onChange={e => onChange(e)}
             required />
            </div>
            <div className="form-group">
            <input type="email"
             placeholder="Email Address"
             name="email" value={email}
             onChange={e => onChange(e)}
             required/>
            <small className="form-text"
                >This site uses Gravatar so if you want a profile image, use a
                Gravatar email</small
            >
            </div>
            <div className="form-group">
            <input
                type="password"
                placeholder="Password"
                name="password"
                minLength="6"
                value={password}
                onChange={e => onChange(e)}
                required
            />
            </div>
            <div className="form-group">
            <input
                type="password"
                placeholder="Confirm Password"
                name="password2"
                minLength="6"
                value={password2}
                onChange={e => onChange(e)}
                required
            />
            </div>
            <input type="submit" className="btn btn-primary" value="Register" />
        </form>
        <p className="my-1">
            Already have an account? <a href="login.html">Sign In</a>
        </p>
        </section>

    </Fragment>
  )
}

export default Register

And this is my users.js

//@route   POST api/users
//@desc    Register user
//@access  public

router.post('/', [
    check('name', 'Name is required')
        .not()
        .isEmpty(),
    check('email', 'Plese include a valid email').isEmail(),
    check('password', 'Please enter a password with 6 or more characters').isLength({min:6})
], 
async (req, res)=> {
    const errors = validationResult(req);
    if(!errors.isEmpty()){
        return res.status(400).json({ errors:errors.array()}); //400 is for bad requests
    }


    const { name, email, password } = req.body;

    try{
        //See if user exists

        let user = await User.findOne({ email });

        if(user){
            return res.status(400).json({ errors: [{ msg:'User already exists' }] });
        }
    
        //Get users gravatar

        const avatar = gravatar.url(email,{
            s:'200',
            r:'pg',
            d:'mm'
        })

        user = new User({
            name,
            email,
            avatar,
            password
        });
    
        //Encrypt password

        const salt = await bcrypt.genSalt(10);

        user.password = await bcrypt.hash(password, salt);

        await user.save();
    
        //Return jsonwebtoken -> this for users to be logged in right after registration

        const payload = {
            user:{
                id: user.id
            }
        }

        jwt.sign(
            payload,
            config.get('jwtSecret'),
            {expiresIn: 360000}, //change to 3600 for production
            (err, token)=>{
                if(err) throw err;
                res.json({ token });
            }
            )

    }catch(err){
        console.error('err.message');
        res.status(500).send('Server Error');
    }
    

});

module.exports = router;

What am i doing wrong? What is the solution to this error?