He’s “busy”

I sort of work with this guy at my job, I’m a delivery driver and he works in the warehouse, I see him for maybe 20 minutes a day 2x a week because we work on different days and I only see him during load out. I added him on Facebook about a month ago and since then he messaged me and we’ve been talking on and off for a month. He works two day jobs so he’s busy which he told me but we’d go days without talking. Everytime I see him in person he’s interested in me and flirting but then he never texts me. One day we were going to finally meet up at his house but then sends me a texts that the reason he hasn’t told me where he lives is because this girl he used to talk to shows up uninvited. He hasn’t bothered to see me or text me and I’m just really confused. I assume he has a girlfriend or in a serious talking relationship but why does he flirt with me and talk to me in person but then never care to text me or see me outside of work? He said he was interested in me and it’s sending me mixed signals and then I can’t stop thinking about him all day after out interaction and then looking at my messages to see if he texted me an unhealthy amount of times. Why do men do this??? Why can’t he just leave me alone in general if he doesn’t want to talk outside of work. Any advice would help. He also did tell me when we first started texting that he doesn’t want a serious relationship but if it leads to it then cool, but we were supposed to hangout last Saturday and then I never heard from him. Just extremely confused.