Past few months(maybe a year) i experience menstrual cramps for 5 days and tiny brown discharge on&off leading up to period(that shortened to 26-27days).then period eventually comes,with very little pain.have regular ovulation.is it low progesterone?

Yes, it could be due to low progesterone with a shortened luteal phase, a condition called luteal phase defect. You should see a GYN doctor for tests.

Low progesterone is unlikely to be the problem, especially if the time from ovulation to your period is about 14 days. Your gynecologist can do an exam and an ultrasound to check for specific problems, but this could simply be normal for you. Menstrual quality and duration commonly change over time.