Late at night, can't sleep What does it mean when guys answer "I think so" about love?

[Sleepless1]

Just finished talking to my boyfriend. We've dated for 8 years but now we are freshly long distance due to circumstance. For the past couple of months he does call me several times a day, but has never once said I love you or I miss you. So I asked him tonight, "Do you still love me?" and he answered, "I think so."

 

What does it mean when guys answer that way? If he really loves me shouldn't he just answer yes? He used to tell me he loves me all the time. What should I do? I just want things to go back to the way it was before.