Fluttering or twitching sensation right in centre above pubic bone. i have ibs and fibromyalgia. could it be associated with either?

Likely neither: Minor and transient muscle twitches are referred to as fasciculations. These can happen anywhere in the body and at any time. Often they are thought to be associated with fatigue, stress, physical exertion, among many other possibilities. But the truth is nobody really knows what triggers these phenomenon. However, it is unlikely to be either ibs or fibromyalgia.

Yes: Yes, these conditions can be associated and in my comments section below i describe these associations.