Depression?

Lately I’ve been feeling super down... like it’s been going on for maybe a month or 2 of just having episodes of just being super sad. I find myself in my room in my bed for long, extended periods of time because i just want to stay away from everyone. I used to never really be like this... but ever since the end of my junior year of high school I’ve been like this I guess...( I’m a senior now). I feel like it’s the people in my life.. but it’s hard for me to get rid of the attachment to these people because they meant so much to me.. idk what to really do anymore. Any advice or anything?