I don't think it's possible to ovulate (or at least get your positive LH surge) when you're on the last couple days of your period... Is it?

Because I took an ovulation test the day after my period ended, and it had a dark line. Not positive, but definitely dark. And every day I take them, they get lighter and lighter. I didn't think to take an ovulation test on the last day of my period, because I was still (LIGHTLY) bleeding. I wish I had a picture of the ovulation tests. Unfortunately I'm at work, and my notebook that has them is at home. But here is my bbt chart. What do you ladies think? I am so confused and would love if people could respond if they have any insight. I appreciate it! Lots of baby dust to everyone!