First day of AF but positive OPK

Jessica • Mom of 2 begins Sept 2019!! TTC 15 months & it finally happened!

Can someone give me some input?

I have been excessively fatigued, lots of headaches, and my appetite has decreased slightly. I was a day late starting my cycle so I took a test...I thought I was taking a hpt but instead grabbed a opk instead and it came back positive. I have some spotting and light cramps. I went and got some first response pregnancy tests, I took two and they were both negative. Why would I have a LH surge if I’m on my period?