An 8 day LP is definitely low. It has to be at least 10 days if not 12 to have a possibility of getting pg. I take prometrium suppositories 200 mg, 2x's/day, about 12 hours apart (although my doc said that isn't so important) from 3 days after trigger until I get a pg result from the doc, about 14 days. I have a 'normal' LP but my doc does it just in case too. Also, do not take it directly following the trigger as it takes about 40 hours to ovulate after the trigger. There's a theory that says that progesterone changes the direction of movement in your fallopian tubes, so I you take progesterone before you ovulate then it could prevent the sperm from reaching the egg. Start taking the suppositories 72 hours after the trigger.