I am sitting here at work with my support belt on after a physio appointment this morning for just this very pain.

What also is supposed to help is avoiding placing strain on your pelvic or lower belly muscles. If you are getting out of bed or from sitting to standing and noticing that your belly is sort of 'mounding' up as you get out of bed, this is because you are stretching your lower belly muscles which can make make it even worse. I'd noticed this and thought it was a cool pregnant belly effect. :-)
The pelvic pain for me is bad after getting out of bed first thing or getting up from sitting down so I can see how it contributes.

The physio suggested to me that if you gently flex and hold your pelvic floor muscle, this in turn flexes your lower belly muscles, hold this flex gently and then move from one position to another - it should help. It won't actually cure the pain but it can help manage it (I hope). Also, balancing on one foot (e.g to put jeans on) or crossing your legs when being seated can make it worse. Looks like I have to change my ways. ;-)