i might have overreacted

so there's this guy at work, let's call him zack. he's not my favorite but we're friendly enough i guess. like i say hi and stuff if we run into each other in the hallway or something. nothing super close, just polite nodding kind of friend. yesterday though, zack started asking me about my weekends and all this really personal stuff that felt weird to answer, like how much i drink on saturdays or anything, so it made me a bit uncomfortable but also kinda annoyed because why would he need to know any of this? we're coworkers, not best friends or anything. so i got a little short with him and told him i didn't want to talk about my personal life and that's just how things were. then later on when i was walking home from work, i started thinking maybe zack wasn't being nosy, just trying to be friendly? like he probably thought since we're both in the same department, i would appreciate someone checking in with me or something. it made me feel kinda bad for shutting him down so harshly, but also i still don't want anyone knowing all that personal stuff about my life. now i'm stuck between feeling sorry for maybe hurting zack's feelings and being pissed at myself for letting some random coworker get under my skin like this. am i just overthinking it or is it really a big deal?