Confusing BBT

Hi everyone! 
I have PCOS and rarely have a 'normal' cycle, but this month my BBT has confused me more than ever. 
Correct me if I'm wrong but it looks like I ovulated (the first spike), but I'm not sure what the dip and then second spike is about?! 
Br most of all, I have had the EXACT same temperature 4 days in a row now (36.51). Has anyone else had the same? Does it mean anything? 
I've checked the thermometer and it is working perfectly fine, it's not stuck on reading 36.51 only. I'm very confused!