If your bbt dips but not below the coverline, can you still be pregnant?

DH and I have been ttc for two years. This is my first month charting my bbt. My coverline is 97.5 and my temps have remained upwards of that for 17 days. Today, 18 dpo, I went from 98.6 (17dpo temp) to 98.24 (18 dpo temp). Now last night I kicked the covers off and woke up freezing, not sure if that could affect bbt. So eventhough my temp dipped do I still have a shot at pregnancy? Oh and btw I've taken a boatload of HPTs and they're all BFN. I went for bloodwork yesterday but won't get the results for two days...so I was just trying to prepare myself...