Is heartburn a symptom?

Krissy • Mama to 2 beautiful boys, 1 angel baby and currently pregnant with #3!
I had a positive opk on October 10th. So assuming that I ovulated on the 11th, I would be 6 DPO today. I have been having AF type cramps since the 10th and today I have heartburn. I NEVER have heartburn. Could this be an early pregnancy symptom? 6 DPO is way too early to test. Since I logged my positive opk, Glow has changed me to a 28 day cycle when usually I'm a 31-32 day cycle.