react native fetch api error with jwt - reactjs

Question

I am trying to implement Jsonwebtoken in my react native app. I followed the video tutorial on their official site and it worked fine. However, I kept getting errors "UnauthorizedError: No authorization token was found" every time I try to make api calls. The api calls all work as expected except I would still get errors like that. I tried the same api calls in postman, they don't give me errors. I found it's possibly because I didn't pass the token back after the api calls?
Here is where I initiate the express-jwt
var expressJWT = require('express-jwt')
app.use(expressJWT({secret: 'I like different tastes'}).unless({path:['/api/users/login', '/api/users/register', '/api/users/register/facebook']}))
Here is where I log in and create and pass back a jwt to my client side
login: function(req,res){
if (req.body.purpose == 'login'){
User.findOne({'localUser.email': req.body.email,}, function(err, user){
if (err){
console.log(err)
res.status(500).json('error')
}
else if(user == null){
res.status(404).json('not found');
}
else{
if (passwordHash.compareSync(req.body.password, user.localUser.password)){
var myToken = jwt.sign({username: user.localUser.name}, 'I like different tastes')
var tmpUser = user.toJSON()
tmpUser.token = myToken
res.status(200).json(tmpUser);
}
else{
res.status(401).json('wrong credentials')
}
}
})
}
else{
res.status(400).json('You are hacked bro')
}
And this is an example of the api calls I make after I log in.
fetchPost() {
var _this = this
return fetch(uri.network.uri + '/api/posts/fetch', {
method: 'POST',
headers: {
'Authorization': 'Bearer '+this.props.activeUser.token,
'Accept': 'application/json',
'Content-Type': 'application/json',
},
body: JSON.stringify({
purpose: 'fetchPost',
latitude: this.state.currentRegion.latitude,
longitude: this.state.currentRegion.longitude,
maxSearch: MAX_SEARCH
})
})
.then((response) => {
if (response.status != 200){
Alert.alert(
'Sorry',
'Unexpected errors!'
);
return
}
else{
return response.json();
}
})
.then((responseJson)=>{
console.log(responseJson)
})
.catch((error) => {
console.error(error);
});
}
this.props.activeUser.token is the token I passed back from the second function in server side
it worked fine and I get the data I want. I also believe I was passing the right token since I tried passing a random token which resulted in incorrect response.
The problem is that I would get UnauthorizedError: No authorization token was found.