does he love me?

Dev
My boyfriend and I have been dating since May. So not very long. I'm typically the type of person that takes a while to have deep feelings for someone. But with my current bf I knew I loved him very soon. To make a long story short::  after a couple weeks of contemplating it I decided to tell him I loved him. I was Leary of it because I feel like the man should say it first but I was 100% sure I loved him & I really felt like he was in love with me as well and had basically told me several times without actually saying I love you. 
So I told him I loved him and he got kinda teary eyed and acted really touched by it and also told me he loved me too. (He's a softy)
So that happened in June or July, I can't remember exactly. BUT to this day when he says he loves me, he mutters it. Like mumbles. It's like he's not confident in saying it. 
I know this man has deep feelings for me. He's talked about us building a house together, our future kids, etc. 
We can be in a phone conversation talking normally and I'll tell him I love him and when he says it back i can't even understand him half the time because he just mumbles. WTF DOES THAT MEAN. We've been saying I love you for a solid 2+ months now. And only a handful of times has he said it with confidence.