Hemorrhoidectomy

I am 6 months along (considered "high risk" due to my son being early and she has a two vessel cord constricting her growth) and have recently had a hemorrhoid become horribly thrombosed. I checked a few moments ago and saw that it is now black and the size of a marble. It hurts to sit and to walk. I've been doing sitz baths daily Bc it has sometimes flared up from when I birthed my son a year and a half ago. It's has never ever been this large and painful. Going on 3 days with it being so bad. I use the extra strength prepH cream and it helps around it but not the actual roid itsself. Im calling my OB tomorrow to see what I should do.. if I can make it that long. I'm so scared of hemmoraging during birth so I really would prefer having it taken care of before I have her. Has anyone had a Hemorrhoidectomy while pregnant?