just feeling under appreciated

I'm 19 and still living at home with my parents and younger brother. Im working 3 part time jobs, so usually about 40+ hours a week right now since my summer started. When I was in school, taking classes at the community college, I still worked between 30-35 hours a week while taking 10 units. I busted my ass to get an A in my classes and worked so hard for it. I've always been a good student, hard worker, and done my share around the house to help out my family. I don't pay rent or anything to my parents, and I am so so grateful for this, as I have some major expenses and live in the Bay Area in CA so it is so expensive here. When I was still in high school, I maintained a 3.95 GPA, was a 4.0 but I missed 2 months senior year due to a baaad accident, and worked 20 hour weeks still, all my weekends went to that. My family has always struggled to make ends meet, and having 4 kids doesn't make it easier. My sister got pregnant while I was a junior in high school, she is 2 years older than me. She never worked hard in school, and while going to the JC I'm now attending, she dropped classes because she couldn't maintain a passing grade at all. She never worked as much as me, and went out all the time to hang out with friends and stuff, while I was left helping make dinner, clean the house, and especially do the thing I hate most: dishes. See, growing up with 3 siblings, there should've been no reason I was washing the dishes every night (no dishwasher) after making dinner and doing hw and working. But my mom said my sister was doing a lot with school and her job, and my little brother had trash and yard work as his "duties". I never complained. Then my sister stopped going to school altogether and I still had to pick up the slack for doing the chores she didn't do. On top of trying to live a normal life as a teenager and have some fun. Summer I worked 40 hour weeks again and spent the rest of my time on my other responsibilities, while she goofed off. Then she got knocked up and I was still laden with more work she suddenly couldn't do. The dishes, again. Apparently it hurt her back too much to stand there and wash them. I have scoliosis, as well as the onset of psoriatic arthritis, and I'm a horseback rider which kills every part of my body. If anyone knows anything about back pain, it's me, I don't remember a day I didn't have back pain. And I fully sympathize with those that do. But my sister has never ever had back pain before getting pregnant, and yet suddenly she was unable at 3 months of pregnancy to do the dishes while I was totally fine? But I'm the "good kid" so I did it. Fast forward almost two years, my sister moved out when my niece was born to live with her baby daddy and I took on even more work. My parents work a lot too so I get it, but my little brother is perfectly capable. And again, he's just like my sister. Never putting in effort to keep his grades up, playing video games and throwing a fit anytime he is asked to do something. He's 2 years young than me, come on! So now, here I am today, working 40+hour weeks starting at 4am and not ending until 7 pm most days, all thru my "summer break". Ik I'm an adult, but I'm also still a teen, I want to have fun. But more than anything I want to relax. My brother has failed multiple classes, been busted for possession and use of marijuana (at school!) and has no job, no license. He takes the trash out in the morning and walks the dogs sometimes and does the dishes 2 times a week usually, I get home and want to just eat shows and sleep. But I have to do more work, especially the dishes. All I want really is for my parents to not make me do the dishes anymore. That's all I want. But I can't ask for that, or it becomes this whole argument about how I have to help contribute to the family and stuff. I take him to school some mornings when I can, bring him home. Take the dogs out all the time. Clean the house in my downtime, not to mention I have a horse that I fully support on my own and have her medical bills and maintainence and general upkeep to do. And my back hurts. I have friends I see once a month practically, unless I run into them at work which never happens. The only thing I do for fun anymore is when my bf is able to see me once a week or sometimes longer, because we're an hour apart and he is as busy as me. I don't know what it was like to live a normal teenage life because I always spent it doing what I could for my family, and even now I do. And I fully agree with contributioning to the family, but when I'm sleeping only about 5 hours if that and working all day then coming home to more, how can I even enjoy my family or being at  home? 
I just want to feel like someone appreciates all I do and have done, because no one gets it, not even my bf.