Positive opk for 10 days???

Charity
I've been tracking my ovulation days and this month I had a positive opk for 10 days straight... How is that possible? I bd for 4 days after my first positive opk but continued to get 6 more positive opk's but wasn't able to bd all of those days because my husband was out of town. But is it normal to have positive opk's for that long???