When a guy hardly texts or calls you does it mean they're not interested? What does it mean?

I always start the conversations. He'll always text me right back, but then sometimes he just doesn't respond at all. I know he's addressed like he wish he had more time to do things with me, etc...What does it mean if they don't text or call back, though if you could you would love to talk to them all the time? Wish you could talk to him, but sometimes don't bother cause most likely he probably won't answer, etc. Also like through texting he always thanks me off and on about things, different random stuff what does that necessarily mean a good thing or a bad thing?