Infinite sadness

I went to a party today, with a lot of people who I am friends with or have been friends with. I've been feeling weird all day, sentimental, overwhelmed with memories from elementary and middle school. And at this party I was dancing with Shauna and Ellie and Mallory and Matt, and everything just sort of split open. I don't know how else to describe it. I looked around the room, and it was like everything was cut out and pasted in its place in my past, present, and future. Olivia and I used to cut out paper dolls from magazines and line them up in careful rows in her living room. It was kind of like that, except with these memories. The sense of time running in a river ceased to exist as well, and the past and the present and the impossible unknowns of the future all seemed to be happening at once.
Most of all, I felt sad... this sort of infinite sadness that isn't like depression, but more of a hollow, empty ache I have begun to feel constantly when I am with my friends, or driving around town. I look at these buildings, and I remember being in them, all the memories of my life in these buildings. I look at my friends and I remember who we were and I'm sad that we've changed, and I love who we are but I'm sad that we will change and that nothing lasts. I guess I'm greedy or something... I don't want things to change. I want them to stay the way they are so I don't ever have to feel sad remembering them.
I hate this sadness. I get it all the time now. I'm constantly aching. For what, I'm not sure. I feel like I've lost everything, even though I haven't, I've just lost the past, but gained the present. The present seems monochrome in comparison to the past on some days, on others it's the other way around.
I think there's something wrong with me. I'm so weird. I had fun at the party, but I was sad. And afterward Ellie invited me to her house where a bunch of my friends were going but I said no. And last night Shauna invited me over but I said no. Part of it is I want to be alone... part of it is I'm terrified of that hollow sadness.
Even remembering fifth grade, I know I was different than everyone else because I thought about the sadness that I felt, and the way it tied in infinitely with the world.
I can't get this e.e. cummings (the best poet of all time) poem out of my head:
in spite of everything
which breathes and moves,since Doom
(with white longest hands
neatening each crease)
will smooth entirely our minds

-before leaving my room
i turn,and(stooping
through the morning)kiss
this pillow,dear where our heads lived and were.
I think this poem is the only way to express exactly how I'm feeling right now, like doom has come to smooth our minds of the past, and I'm leaving a room, or my town, or my childhood, or something abstract and ungraspable, and all the memories of how we lived and were, how we existed, how we breathed and fought to survive, are so powerful that the only thing that I can experience from them is their collective concentrated sadness.