This is fairly uncommon. You should contact your school's MSTP director to check if this is an option. May I ask why do you want to get a PhD after your MD/DO? You do know that you can do research without the PhD, right? When you become an attending, if you spend 80% in clinical, that PhD won't be worth it -- I paraphrased that line from a MD/PhD attending.
Anyone have any experience or knowledge if there are accelerated programs towards PhD for M.D./D.O students once I've graduated? Or any other comments? Or is it basically I need to ride the whole way through?
There are no real legitimate accelerated PhD programs for physicians. That being said there are plenty of research fellowships in many specialties for you to do to essentially compensate for a lack of a PhD.
At my grad school, the PhD part for the MD/PhD part was ~ 3 years (sandwiched between M1/M2 and M3/M4). The PhD earned by our med students was more like a glorified MS degree.
I once dated a woman who got her MD/PhD at Baylor. Now there, your PhD is a just like a typical PhD...meaning it will take some 5 years to earn!