ERR_TOO_MANY_REDIRECTS agreestat.net redirected you too many times.

Hi, I just set up SSL with my web app following the instructions provided in the document "https://www.digitalocean.com/community/tutorials/how-to-set-up-shiny-server-on-ubuntu-16-04." But since doing it, I have been getting the error “ERRTOOMANY_REDIRECTS”. Would my NGINX file be the problem? In case it can help, here is my NGINX file:

server {
   listen 80 default_server;
   listen [::]:80 default_server ipv6only=on;
   server_name agreestat.net www.agreestat.net;
   return 301 https://$server_name$request_uri;
}
server {
   listen 443 ssl;
   server_name agreestat.net www.agreestat.net;
   ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
   ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
   ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
   ssl_prefer_server_ciphers on;
   ssl_ciphers AES256+EECDH:AES256+EDH:!aNULL;

   location / {
       proxy_pass http://67.207.84.153:3838;
       proxy_redirect http://67.207.84.153:3838/ https://$host/;
       proxy_http_version 1.1;
       proxy_set_header Upgrade $http_upgrade;
       proxy_set_header Connection $connection_upgrade;
       proxy_read_timeout 20d;
   }
}