Why feeling so down these days

I am 21(f) I live alone and these days there have been really ups and downs in my life. Like not big or not small ( but does it matter) it's like I have been crying, feeling down, not really wanting to do anything at all.but I need to study my exam is literally so close. I know I can't waste time. But I don't really want to do anything, even if I want to, my body and my mind is not supporting me to do so.

My eyes are literally swollen. Maybe it can be periods. But I don't know

What to do!?