Help?

So I have struggled with this continually for over a year now, but it gets especially bad when my mood takes a turn for the worse or I'm very anxious, but I didn't know where to post this, so I'm making it a note.
I keep getting a feeling that I'm not really here. I feel like I'm dreaming almost all the time. It's pretty scary sometimes. I feel like I'm going crazy when it happens. I have actually dug my nails into my skin to feel it sometimes because the feeling that I'm dreaming is so intense that I feel like I can't even feel my body. I get very spacey too and can't concentrate on anything. It makes school very difficult sometimes. I feel empty emotionally when this happens or I'll just constantly cry.
Sometimes having something physically to hold helps but other than that nothing helps me. I also get very clingy and want to cuddle with people (it helps a little too) but I know I can't rely on others. I have been told to try breathing and concentrating on like my feet on the ground or the sight of something but then I start doubting that I'm even feeling or seeing it and I get scared which makes it worse.
Does anyone else experience this? Does anyone know what can help me? Or where can I post this where someone WOULD know?