PG::ConnectionBad FATAL: role "Myname" does not exist

I am trying to use PostgreSQL so that I can deploy to Heroku. However I cannot run localhost anymore why? I get the following message:

PG::ConnectionBad
FATAL: role "Myname" does not exist

Here is my databse.yml

development:
  adapter: postgresql
  database: my_database_development
  pool: 5
  timeout: 5000

test:
  adapter: postgresql
  database: my_database_test
  pool: 5
  timeout: 5000

production:
  adapter: postgresql
  database: my_database_production
  pool: 5
  timeout: 5000 

Here is my gemfile:

source 'https://rubygems.org'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.0.3'

# Use pg as the database for Active Record
gem 'pg'

# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.0'

# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'

# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'

# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'

# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'

# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 1.2'

group :doc do
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', require: false
end

# Use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.1.2'

# Use unicorn as the app server
# gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano', group: :development

# Use debugger
# gem 'debugger', group: [:development, :test]

gem 'rails_12factor', group: :production

It seems that pg needs me to create a user or databse however I am unable to or don't know how. Couldn't find any commands that worked for me(I'm on a windows btw)

What can I do?