Just do the simple math. Your company received $2mm months ago and has 15 employees. This is ~$134,000 per employee for a year. We'll imagine they will push towards a Series B round within 12 months. They are receiving $1,000 per month in revenue. I'll assume you mean gross revenue here, net would be a different calculation entirely.
With that math in mind, imagine the salaries, benefits, employer paid taxes, equipment cost, and office (per employee). Assuming that is 100% of their costs (we didn't even talk about infrastructure costs, marketing, accounting, legal and the meriad of other costs associated with running a startup), does this add up to more than ~$134,000 per year per employee? I would imagine the answer is yes. So, yes, they can't afford to give you more. Frankly, they can hardly afford the employees they have now. In my view, that's a really tight budget.
What should you do? Well that is a really personal question. If I were you, I would decide if you would like to stay or not, but don't blame them for being good at figuring out the math of the situation. They are on a shoestring budget, I have zero doubt of that. I would most certainly tell you that "we can't afford it" right now, if I were them.
Now, if they are making $1,000 per month net revenue, then they are profitable. That would be a different situation entirely and they could actually give you more.