How to really tell if the guy is interested in you?

I am really unsure on if this guy, I have known for a week, and gone on 1 date with really is interested in me or not. We had our first date this past weekend and it went over really well. The day after the date, which was Saturday, Sunday arrives and he doesn't text me until around 7PM. I replied and never got a response. So I decided to text him again to say good night around 10PM-11PM and from there we talked briefly over texts. Today arrives and by 12PM no text messages when last week he would text me in the morning 9AM, 10AM, 11AM, or even 12PM and nothing from today. So I decided to text him around 12PM, seeing how his day was going, then texted him other stuff I was doing, and even sent him a link to buy the tickets for the movie, we are suppose to go see this weekend, for our 2nd date. But to me, it feels like we were texting and talking so much more last week and since our first date, our talking has died down just a tad and thats hurting my feelings. This guy says he really likes me a lot, and wants us to go on this 2nd date and is interested in me hands down, he had said during our 1st date. But then again he is hardly talking. So do you think he is still interested or is it fading away? I really don't know.