A speech therapist can help you with this. Ive seen many people go to one of them and it has helped them tremendously.

As far as explanations, you dont own anybody anything. Im sure you are being self conscious and your speech is alot better than you think. You dont need to disclose your medical history to anyone, especially at your job. I wouldnt say a word if it were me. Speaking used to be what I did for a living but I wasnt able to do my old job anymore after my 3rd round of OC. This was mainly due to my mind not being quick enough to keep up with everything, my speech was secondary to why I left my job.

If you must say something, make it very brief and then drop it by talking about another topic. If anyone questions you then just politely say you prefer not to discuss the details. Some insensitive people still may question you then just say "its not anything to do with _____ , which is more important right now"(whatever your topic of discussion was). What you said was perfect about having oral surgery recently and then just move on to whatever you needed to talk about.