You deserve far greater compensation than you currently receive. Given the economic constraints of the firm, you shouldn't be paid significantly more.
Every negotiation is a competition between contrasting views of reality.
To be paid what you deserve, you have to persuade your manager that your version of reality is correct. Instead, we're all compensated based on market demand - what others in the market are willing to pay for our services. To earn more, you must show your company that your market value is actually greater than your current salary. To do that, find out what the market is willing to compensate a person with similar experience, tenure, skills, and credentials. Target organisations that matter to your company - firms that it uses as benchmarks.