Help- future bfp??

Rose 🌹
I took one of those Amazon cheapie HPts this evening. 
I forgot about it for about 30/40 mins then came back and there was a definite faint line. Hubby saw it too. 
Within 10-15 mins of jumping up and down excitedly together the line had gone. 
Has anyone had this? Are we still in with a chance? 
This is my chart....as you can see I had a massive temp drop yesterday. Possibly caused by my thermometer acting up.