The detachment you are talking about is called "Depersonalization" , or maybe even "Derealization" in some instances. Depersonalization is the sense that you are not really human. Derealization is the sense that the world around you seems distant, dreamlike even. It is often found to go hand-in-hand with "anhedonia"-- a lack of ability to find joy in things once found to be pleasurable. Usually this is a symptom of depression. Don't trip--hormones are ever-changing when we are in our 20's (which is why I can empathize, I often feel this way). If you study pharmacology at some point you might find out that hormones and chemicals in our brains are responsible for the majority of our emotions. How else do you think a THC molecule could alter our consciousness so radically???

Bottom line: It's all chemistry (not to trivialize your feelings).