Why don't I care about much of anything?!!?!?

Okay so recently, people have been able to notice this. Everyone I talk to can tell I just don't care. Like I don't care about anything. I don't feel sad or anything but I just don't care about much of anything. Like I take care of myself and everything it's just. If my boyfriend or someone comes to me with a problem... I don't care?!?! I am deffinatly not acting like myself and I can even tell, which is why I'm posting this question, but I just can't get to the root of it.. For example. This person told me that this kid that likes me was going around saying I was sending nudes around, I got really pissed, but then I got to the bottom of it and I just didn't care. I'm moody, but I don't care. What's wrong ? Am I the only one that feels this way? D: