Hi, while I concur with everything already posted, I just wanted to add some more information that may be relevant. At your age, you're in the right demographic to develop a mood disorder such as depression (~10-15% of population), or bipolar disorder (1-3% of population). Just to mention, bipolar does not appear in real life as it does in the movies. Most people spend most of the time either healthy or depressed, but different medication is used since risks are different. As already suggested, keep track of your cycles.
BTW, apathy never killed anyone, and a little bit can actually improve the lives of overly stressed, type-A, over-controlling individuals, IMO. But you did not present yourself as such, and "overwhelming" is a strong word. When emotional bumps in the road cause problems in functioning (which you don't mention), or cause distress (which seems to be the only problem you have now), they cross over into medical problems, and medicine can help, either in the form of counseling, or medication.
Emotional "growing pains" are common (though more so in puberty, I think), and this all may go away. But keep your eyes open, long term. You know yourself best, and you are your own best advocate. BTW, if anyone diagnoses you as depressed, look for a "blue light" or "mood light" as an alternative to medication, especially so if your apathy keeps happening in the fall/winter when days are shorter.
Good luck!