How to avoid petechiae

So I've been pumping for close to 8 months on and off, mostly for recovery from petechiae, the little red dots. Early on I didn't ever experience it and slowly worked myself up to the point where I could use 8in hg for 5 min sets.

Then it started happening all the time. I take a break to recover, about a week, and I'll restart at 5in hg for 2min sets. Recently it has been happening every time I get to the point of 7in hg. It takes 2-3 weeks for me to build up to that pressure. Am I just moving too fast? Does this happen to anyone else? Appreciate any advice it input.