Strong blood flow when meditating

I am currently following a vipassana retreat at Panditarama Lumbini (where you are asked to notice the rise and fallings of the abdomen). The first 5 days were OK (even if I maybe was pushing too much with crossing the legs, hurting for one hour periods) but I have a problem since two days ago (even if I stooped pushing hard crossing my legs): When I sit down for meditation, my blood flow increases so that I can feel it everywhere on my body including head and abdomen, to the point that I feel both the breath and the blood flow when putting the hand over my abdomen. Also, I started salivating a lot (only when I sit down for meditation). Also after only one or two minutes of starting the meditation, my breathing speeds up (instead of speed down as usual). I have had this problem already for two days now. What can be the real problem and how to solve it? Shall I stop the retreat? (I feel that stopping now the retreat without having experienced a nice insight would be a bad idea because I probably wouldn't retry the retreat never again)