You will need to be tested by a force senstive person that has the skill to see if you are FS. Generally the faction your in arranges a test every so often.
As for when you become FS, yes. Though it would be lvl 6 not 7 because of when the chances are run. If you become FS at a higher level you will not be as powerful as someone who was FS at a lower level. However, when you are tested does not make any difference in this case.