How do i know if im been discharge from DEP for the marines so i can go join another branch?

If you have been told you have than you probably have. When you talk with another Recruiter they will be able to check. Your new Requiter will have you sign a form that will have your MEPS info made available for the new branch you are applying for. When they summit this paper MEPS will know ir the Marines have released you. Until you are released your new Recruiter won't have access to your MEPS info, (your ASVAB scores and Physical info) all other parts of you packet will have to be rebuilt.