Help! Bbt low - positive hpt

Tara • 02.22.16 ZJLA Baby #2 is on his way!!!!
My bbt was 97.83, which is a slight decrease from yesterday. I'm a day late with my period. So I took a hpt (or ovulation, not sure lol) test today and it's positive. A very very light positive though. I'm going to go buy more today. But what does this mean?? Should I be worried?! Because I am.... Please help.