I don't wish that my source code be available for download at launchpad when i upload my packages for building. Is it possible?
No, it's not possible. The source will always be publicly available for any packages you build using Launchpad as a regular user.
What you want is only possible if you get a commercial subscription to Launchpad and use its "private PPA" option ($250/year).
If interested, please see:
It's possible to build packages without using Launchpad for building by using your own computer.
Among others the
Here's a link on askubuntu with some details: Getting set up with git-buildpackage, pbuilder, etc for software packaging.
Of course you will have to find a way to distribute the debs that this produces.