Positive OPK cd23

After testing up until CD21 with no positive, I had given up hope and stopped testing. But I have been having cramps the past few days and cm became watery so I decided to test out of curiosity this morning and got a blazing positive! Now I am worried that I could have got a positive yesterday when I didn't test and missed the start of my surge. Does that matter? Will I still be in with a chance if I DTD today?

Is it even common to get a positive this late in my cycle? I have no idea what my cycle length is as this is my first period in a year and they have always been irregular.