"
And if I bleed
I'll bleed
Knowing you don't care
And if I sleep just to dream of you
And wake without you there
Isn't something missing?
Isn't something
"If I bleed I'll bleed knowing you wont care" This signifies how they feel. They think no-one could care less about them, and the mention to bleeding is saying they self harm and don't think anyone cares.
"And if sleep just to dream of you and wake without you there." This is that there is always someone there thinking about, they sleep just to dream of them, they care about them, but don't think the other person cares.
"Isn't something missing? Isn't something" This shows that they feel abandoned, uncared for. The missing thing is care towards them, love, friends, family. The part where it says isn't something then cuts off is like them stopping from pain of hurting themselves.