Me serving . http://youtu.be/We_qtfTKO6c
. Sorry it's not very good lol . The court was wet so I did the best I could without falling over .
I think you really could benefit from coaching - either a pro or a friend who knows the fundamentals.
You are not getting a full extension on both your tossing and hitting arm. Your shoulder (and hip) turn is inadequate, and you're not using your legs. All these add up to a pretty weak serve. You also have a hitch in your swing but it may resolve once you have the proper motion.
Do you realize that you move your front foot so that you end up mostly facing the court before you even begin your swing? That inhibits the shoulder and hip turn. You might want to position your back foot behind your front foot (it's hard to describe, but facing sideways on the court, take your back foot and move it a little behind you).
When you toss the ball, don't drop your right arm (since you're a lefty) too soon, make sure you're getting a good extension with it. This will help with your full service motion because you'll drop your left shoulder.
You break your wrist during your swing (i.e. you cock your wrist so your racket kind of flops back behind you). In a normal service motion, the racket naturally drops behind; there is no need to actively cock the wrist, it simply remains relaxed until the pronation right before the ball strike.
Again, try to get full extension as you hit the ball - tossing it higher will help.
There are lots of instructional videos on YouTube showing the proper service motion, but it really helps to get someone who will correct your particular issues.