Worth

Here's a little secret about life that many people don't know. If you have half a brain, if you can figure things out and have some sort of ethics, you are a hot commodity. The world literally needs people like you or it will stop working.
This planet is full of people that don't give a shit. People that don't know, and don't want to know. They skate through life, playing dumb (and sometimes not playing) so that others will do their work for them. The only effort they put into anything is to get out of putting effort into anything else.
These people tend to resent others that appear smarter or more competent than they are, so they ridicule them from an early age. Sadly, if you have half a brain and all the other stuff, you also get ridiculed by people that are above you in society because those people are insecure and feel threatened and want to keep you down.
So you end up feeling like you're not worth your true value. You work at your job, and get more and more responsibilities heaped on you because it's easier for your boss to just get you to do it then try to motivate some lout to do their own work. You feel some strange loyalty to your employer to do things right, but even more than that you can't see doing something half assed because what's the point of doing it at all then? You possess logic and empathy and a sense of duty to yourself, rare and admirable traits that often make you feel like a sucker.
You end up working harder and for less money than you're worth, because whether you realize it or not, all that shit people have been giving you all your life has done exactly what they wanted: you don't know your own worth.
Like I said, you are a hot commodity. Employers love people like you, hard workers who don't know what they are worth. Lazy employees love people like you, hard workers that do their jobs for them.
I have been that all my life, but I have never hesitated to ask for raises or promotions or whatever other perks I wanted because I figured out my own worth. I got them every single time. If you can get just a little bit of confidence going, the world is your oyster. Employers will not let you get away, and they can spot people like you when you apply for a job, so don't let them take advantage of you. They actually respect you for asking. It means something to them, you have to prove you have backbone and drive.
Demand what is fair, don't let them cow you into thinking you should be grateful for them letting you work there. You are probably doing a bunch of different jobs that aren't even in your original job description. They need you as much, if not more than you need them.
I know about this issue on both sides of the fence. I have been in management positions too, and I was pretty much told this exact thing by business owners and other people in management. Also, keep this in mind: I'm a business owner and an employer telling you this.
So demand what you’re worth, and not just at work, because no one else is going to do it for you.