The CSS Profile has a section for “special circumstances.” This would cover things like a parent losing a job, unexpected health expenses, a sibling with a special need, a natural disaster, that kind of thing.
Harvard’s aid is very generous and pretty transparent for most students. If your family makes under $65k it is free, under $150k and you pay 10% and there is sometimes aid over that figure, but $150k is the figure quoted by the department.
There is nothing wrong with meeting with a financial aid office. I did that for one of my kids at another Ivy that is not as generous. I basically told them I did not want to encourage my son to say yes if we could not pay for the whole 4 years, and I also said I was concerned about grad school. They had some helpful things to say, and were very welcoming. Just tell the Financial Aid office that finances are a key part of your decision and you want to see how it will play out over the 4 years before you decide.
I would not have high hopes about negotiating an increase though. I would expect advice on how to make it possible, what jobs might be available (I agree with Telluric on this) and so on. And no, you are not obligated to work; those potential earnings are simply charged to you if you don’t.
Summer jobs may be able to help with expenses. One of mine helped pay tuition because his area of study offered good internships every summer. Research assistant positions are sometimes available depending on your field.
Harvard is a great experience but there are other schools out there that also offer a great experience.
You are not the only young person who has come on here feeling badly about the cost. Sometimes, it turns out, those feelings are not warranted and the parents aren’t aware the kid is struggling with them. I strongly suggest you raise you concerns with your parents. They may reassure you so that you feel better about this expense. Harvard and some of the Ivies have incredible financial aid and you are unlikely to go elsewhere for less, unless a state or other school offers a full ride for merit.
Congratulations on getting in and my wish for you is that you can attend Harvard after talking with your parents and feeling better about the cost.
If you and your parents decide otherwise, it will work out fine too. But it does sound as if your family can pay and sitting down with your parents may very well help you accept that.