If I may ask, what makes you think you have over watered/fertilized? Explain what you mean by thicken it up?
Can you post a current photo?

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Ankraras - Hi. I posted earlier when I wasn't sure what kind of lavender it was and people said from the picture it looked over-fertilized and over-watered- (http://forums2.gardenweb.com/forums/load/namegal/msg051158049963.html) Thanks...Hope you can help

The photo is out of date and I lack imagination as to what this plant may look like today. My opinion is based on the photo you provided.

To me, it looks like your plant is growing in just a bit less than idea conditions. The growth appears to be reaching for the light but this
can easily be corrected by a change of watering frequency together with allowing more light to reach the plant. It makes sense to me to
place the plant where it would receive the afternoon sun. In it's current location I would move the plant in front of the screen or remove
the screen.

You must be sure that the plant gets enough water, that is when ever the plant needs water it must be watered thoroughly until the water
is pouring out of the drainage holes. Lavender in general likes the soil to dry out slightly between watering and the best way to be sure
when your plant needed water is check the soil.

I would not worry about timing for now thus allowing the plant the opportunity to show off it's best quality. If you are still displeased with
it's performance post again in the spring. We can go from there.

Frankly, your plant looks to me to be a perfect candidate to be trained as trunk braided together to a tree like form. If you would prefer to
leave it as a clump style it is simply a beauty of it's own also. This is just some ideas for your thoughts for future development.

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Ankraras- Hi. They're just around 13" tall at the highest branch and thin. I have it outside where it gets direct morning sun until around 11am and then indirect the rest of the day. I will start watering it with more water. Are those long metal soil moisture meters that you stick into the soil any good?
I have another lavender that I bought, to show mine what it should look like, which already has flowers. It's the same height as mine but a bit denser/thicker and with flowers.
What would you suggest as to whether I should grow it in "tree-like form" or "clump style"? Are there any advantages or disadvantages to either? Thanks for your help. I appreciate it.