My colleagues are rich people ! Help !?

I'm a 33 yr old, female uni lecturer. I accepted this new job because it pays well. I need the money to pay my car and flat. However, I just envy my friends who buy only branded stuff and have 2 credit cards. I have none and have to really save money for my expenses ( I have two kids as well). I only shop at the hypermarket for my clothes and shoes. i feel small everytime I go out with my friends.