My parents are forcing me to share a room with my sister. Am I overreacting?

My (20M) parents moved my sister (12F) into my room. A little bit of background info:  We're a family of five: parents, 26M, me and 12F, living in a three bedroom house. As children, my brother and I would share a room, and then I would share with my sister. When I was 16, my parents moved my sister into the lounge, it was a room we hardly used. That way, each child had their own space. Recently while I was at work, I came home and my sister was moved into my room. No warning or prior conversation. As a teenager, I battled with depression and suicide, I also experienced heartbreaks and my grandmother's passing (she's the person who raised me), Because of all this, the room had many negative feelings tied to it, a month or two ago, I spoke to my mother about how I feel about the room. She said that I can swop rooms with someone.  Of course this never happened and they went ahead with moving my sister in. I just feel so disregarded and I feel like I don't have my own personal space anymore. I have zero privacy and because of the big age gap ajd many differences,  my sister and I are always clashing. My depression has came back and I have not had the motivation to clean the room. It has become messy and now my parents, and brother have resorted to making me feel guilty and calling me names. I wish I had the means to move out, as this is really affecting my mental health. Any advice would be appreciated