Why did my boyfriend just stop talking to me for no reason?

I have been with my boyfriend for almost 4 years now, for the past few months we have been in a complicated relationship it was just starting in May that things were starting to get really good again I was happy with how the relationship was going the last time I spoke was on the phone last we Tuesday, when we were talking the conversation went really well we didn't have any arguments or anything of that nature we ended our conversation on a positive note, the next day I called and he didn't answer I figured he was busy, he didn't call me back at all, I usually see him on the weekends but this weekend he didn't call at all to see me, I thought he mustve been really busy but now that's its been more than a week I don't think he could possibly be so busy, I usually don't do this but I called with a private number to see if he would answer I was just curious and he did. I'm so confused why did he all of a sudden stop talking to me everything was going so well its obvious its just my phone call why would he do that, should I text him and ask him I don't know any other way of getting in touch with him, we never really text we always talk on the phone so I don't know if I should text him about this.