Options for tightening the neck.
First of all dont be too hard on yourself. We all have a double chin if we tilt our head down too much. The options at your age would be some gentle liposuction or a minimal platysmaplasty. The later procedure in addition to removing the fat can also tighten the underlying muscle.
You appear to have some small fat deposits (even though they may not feel like it to you) under your chin. In someone your age whose skin is still very elastic, liposuction is probably the best option to remove this and allow your skin to "shrink wrap" around your neck. This avoids a formal neck surgery and is great for patients with anatomy like yours.