Is it odd for me to feel this way?

Since I was a preteen, I have to set aside at least a few hours of alone time, or i get very testy. I could be around the happiest, most fun people in the world and still get so annoyed that I have to start a fight so that I can be alone. Lately, though, it's been different. I can't help but pick apart people's issues, which gets them irritated at me and strains relationships. At the mall yesterday I suddenly felt as though the building was much too small, that I knew the place too well (and I haven't been there in months) which made me think, randomly, "I can't keep doing this!" and just felt numb for the longest time. Not sad or frustrated, just empty. I have no idea why. That, and now every little thing annoys me, from the cornyness of commercials to the sound of a person's voice. The only medication I take is Ridilin for my ADHD, and this is my second month with it. I also found out that my uncle has stage 4 bone cancer, which could be one reason why I'm feeling like this...that, and depression runs deep in my family. Wow I feel like I'm talking in circles...I guess I'm wondering, what are your thoughts on this?