Your options narrow considerably after a poor performance in a structured post-bacc or SMP. That being said, the fact that you are shooting for DO does help matters.
You could (1) Apply to other structured postbaccs/SMPs (2) Continue in your current program and take classes to boost your GPA there (3) Retake some of the classes that have pulled your GPA down at a 4-year institution as an informal postbacc.
Another SMP/PB with decent linkage would be the fastest option, but be aware that it will be much harder to gain entry into one of these programs when they can see that you've performed poorly at one already. Also, it could very well be the nail in the coffin if your study skills don't do a 180. The purpose of Option 2 is to cut your losses regarding linkage to your postbacc's med school, but to at least salvage your GPA there so that you can leave with a decent-looking number on your transcript. Option 3 takes advantage of the grade forgiveness policy of DO schools - it will require more time, but it will raise your GPA.
If it's feasible to stay where you are now for another semester or year so that you can leave with a decent GPA, it'll keep more doors open. Depending on other details of your application, that alone could get you into a DO school. If not, another SMP or an informal postbacc could take you the rest of the way. First and foremost, as others have said, fix your issues with studying and/or test-taking. An SMP, post-bacc, DO school, MD school, the Caribbean - none of these will remedy the problem. Better to fix this now than to find yourself ill-equipped in med school.