I've been having pain on the left side of my stomach followed by constipation and low grade fever 99.9. i do have diverticulitis is this a new flair up?

Could be: Pain the left side of the belly can certainly be caused by constipation. You don't need to have diverticulitis to have that pain. A temp of 99.9 isn't scary in someone who is otherwise healthy. It's reasonable to get the bowels moving with a laxative and see how you feel. In someone with a history of diverticulitis, have a low threshold for getting checked.

Sounds like it: Please check with your doctor to get you on the right RX . It is diverticulitis until proven otherwise