Always talk about what you can offer, never what you need.

What can you do if it doesn’t work out?
You can ask your boss for a day to reflect on the outcome of the conversation. That buys you time. The key now is to analyze: what led to the failure? There are only three possibilities—the fault is yours, the system’s, or the role was never the right fit for you.
If it’s your own mistake, take note of it and learn from it. Go back to your boss in three months.
Maybe the problem isn’t you at all: you did everything you could, but your value still wasn’t recognized. In that case, you should look for a new job as soon as possible. Don’t undersell yourself!
But be careful: your value may be acknowledged, and they may be willing to pay you more—but simply can’t. Sometimes there’s just not enough money. In this situation, you need to weigh things carefully: how important is staying at this company to me? Is the current financial difficulty temporary? What other benefits does the company offer me besides money—for example, how much can I learn here?
If you still want to stay, there’s a simple way to get compensation that reflects your true value: you can propose keeping the same salary but working only seven hours a day instead of eight.
You can use that free time to earn more money from other sources. You could invest on the side, work like an entrepreneur, or make the most of the time to establish yourself as an expert. Who knows what kind of opportunities might arise… Perhaps having more time right now is more profitable for you than earning more money.