BBT Spike 11dpo - 4 days until AF

Ka
What is happening? I've had a temperature spike today (noted by glow) but I'm 11dpo and 4 days away from AF so I haven't ovulated 🤔 shouldn't my temperature be lowering now not spiking? 
Any advise on what this could mean? I feel well and no changes in sleep etc. 
Thanks ladies xx