Weird Period

Bunni

So were trying to concieve and my last period was only 1.5 days long. Now at 10 days though In having pink brown spotting and cramps . (Not pregnant)

Im due to Ovulate in about 5 days. Opk tests are negative so it isnt early ovulation spotting. Has anyone experienced this or know possible reasons? Wondering if its to do with my age (41.5)