Hi Estee,
I can totally identify with you. I have a fear of abandonment, and I think it's a rational fear, especially when you open yourself up to someone and get close to them and then they leave. I think it's also normal to build up a defense mechanism (like you said, you turn on the "I don't care attitude") to avoid the pain. It's always hard when we feel so strongly and then feel as if we meant nothing to the people in question.I wish I had an answer as to how to get over these fears, but all I can say is I understand, and you are not alone.

Hugs,
Sujin