If he's not interested, why does he randomly call to see what's up or invite me out?

I met a guy about 6 weeks ago while I was out with friends, and we hit it off and exchanged numbers. He called the very next day to see what I was up to, and we talked or hung out a few times each week for the next month or so. Long story short, I haven’t heard much from him the past two weeks and I assumed he lost interest, which is fine- that’s life and I’ll get over it.

But, I’m so confused because either a) I’ll not hear anything from him for 4 or 5 days or b) he won’t respond to me asking him what’s up, but then I will randomly get a text asking how my weekend went, or even a heads-up that he’s going out with some friends and I’m welcome to join. If he has lost interest in me, why is he still making an effort to see how I’m doing or inviting me out? If he actually is still interested in me, why don’t I hear back from him?