Help understanding my BBT chart

Hi, I was just wondering if someone could help me understand my bbt chart. This is the first one I have recorded and from reading information about it I thought that during your fertile window it was meant to rise but mine seems to be continually dropping, and was random before that. I am taking it at the same time everyday before I get up. It is however to a tenth of a degree instead of a hundred but surely that wouldn't make this much of a difference? Any advice would be really helpful. Thank you