What is going on with me?

I'm 18 and don't really feel like going out anymore, I stay up until 6 am basically doing nothing, but I wake up at around 2ish every day. I don't want to go out with my friends anymore, I cry about everything, like literally. I'll remember something sad, and I'll start randomly crying. I'm very emotional to everything now, and I wasn't like this a couple months ago. I don't know how to handle situations lately either. I'll either get really angry and do crazy things like punch walls, and just go insane or I'll start crying and won't stop for 2 hours. This has been going on since April. I don't know what's going on, and I don't want to go to a doctor because it's not something to worry about, I just want to know what's causing this or why I'm acting this way all of the sudden.