Salary Benchmarking against my peers

There were a few occasions when i met up with my peers from poly and when they were discussing how much they earn, sometimes I feel like i’m underpaid. Not sure if anyone felt the same way before. The thing is, all of us have worked the same amount of years but I have no luck in finding a higher paying job. They have all stayed in most companies for 2 to 3 years while I have been in the company for 5 years, yet getting paid lower than them.

How can I get to where they are? Open to any suggestions