Blood pooling at one part of incision

I'm 3 months pp. This is the third time I've had this "blood blister" pop up and then bust on one part of my incision. It doesn't hurt. It just turns purple, then a black color and then pops and bleeds for a while. I don't know if this has something to do with an internal suture or if just part of my incision can't heal BC of my belly flap over it causing friction and moisture. Any one else have something like this happen?