I work on a dod job right now does that mean I have security clearance?

Yes, most likely it does. Depending on the sensetivity of the work involved the security clearance can change over time.

Do you have to be a citizen to work on dod jobs

Depends on at what level your working. For many yes.

No you do not need a security clearance on all DOD jobs. It depends on the job. You need to read the job announcement for the qualifications needed for the job you are applying for.