Hi Irhyper2. Without seeing your swing it is very difficult to make any constructive observations. However, at your age and being reasonably fit, you should be able to hit the ball another 10 yards without swinging very hard at all. Usually, the reason for lack of distance is coming over the top (from outside in) and hitting the ball with an open clubface. I assume that you have played for a while and that you have learned to compensate for the outside-in swing by leaving the clubface a little open so that the ball starts in the right direction (sometimes, the opposite happens and the outside-in swing compensates for the open clubface). One clue of an open clubface might be that the ball flies a little higher than usual. Only you (or, probably better, a pro) could tell you that.

How far the ball flies, is dependent almost exclusively on the clubhead speed, the angle of the clubface and the swing path. You might try to shorten your backswing (without losing your timing) but making sure you turn your shoulders far enough and shifting your weight to the left as the first move in the downswing. This will take some practice if you're not used to doing it that way! Remember, most of the clubhead speed is generated in the bottom half of the swing and much of that has to do with how the clubface rotates through the ball. As I said at the start, I don't know your swing but this is probably good advice for almost anyone.
Good luck, and keep swinging!