Can't take it anymore

Hi i'm 21 y.o and i'm really worried about the state in family the last 5 years.

My mother is really depressed, she doesn't feel like doing anything, but my father still does everything as she was the same as always, we keep going anywhere my father wants to , spending the time as he wants, but my mother always feel sad anywhere we are. I agreed with her that maybe we shouldn't do so much things together as it only leads to unhappy experiences and discutions. Instead we should work on her state until we find what is making her so sad, she seems to be happy when we are just doing daily stuff like working, talking about anything irelevant, but the moment we take her free time to be as a family she doesn't seems the same.

They have 2 sons and a daughter, me being the oldest. My brother (he is 20)is really bad at studing and has to take a lot of time on it to pass a simple exam, that leads to lots of discutions with my father. My sister, as my father wants to have time as a family(she is really 16), she doesn't understand the situation and is being really mean with my mother, telling her things like "why dont you want to do anything" or "you are so boring". Im sure she will eventually grow up and think about how bad of a time my mother was having all this time.

I'm studying university and i've been feeling anxious for 2 years now about my family situation, i've been the only one who went to a psiquiatrist(don't know if thats how you spell that) and I was told that i had severe depression due to this situation, still even if i knowledge the problem, I can't change a thing.

I talk every now and then about this with my father, but even if he seems to understand it he is still doing the same things over and over again.

Today we were going on a trip he didn't tell us about it until a day before and me, my mother and my brother didn't feel like doing it a lot, we had plans and we were going for 11 days. We started arguing for a long time and ended up talking about my mother's problems and how sad everyone was about the whole family situation, it was the first time anyone apart from me stated that we were not okay to my father.

In the end my mother cried and we are still doing the same plan as nothing has happened. My father wont listen me or my brothers cause we are his sons and he doesn't respect any advise from us. And my mother just explains him why is she sad and why she doesn't wants to go anywhere, but my father after listening it all just tries to calm her down and keep the same plan.

I don't know what to do, i don't even think my father is even fine about all this.

I tried to convince him to go to a psichologist but he told me to never tell him that again(he was really angry about it, his family had a lot of mental illness cases and they all were pretty tought so he thinks that telling someone to go to a psichologist is the same as saying they are totally out of their mind)

I can't stay like this, I just feel like something real bad is going to happen if we don't do anything about and I get a really strong pain in my chest whenever I hear him raising his voice at anybody, can't focus, can't enjoy on my own, can't think about anything, please help...