9 DPO BBT

So my partner and I have been TTC for 15 months. We are beginning the tests for IVF as our fertility specialist doesn’t feel IUI would work for us. We are still trying to conceive naturally in the mean time. I have been temping and typically experience a bbt dip 7 DPO every month. My temp usually goes back up to the temp it was at before the drop then around 12 or 13 dpo my temp drops again and I get my period that day or the next day. Since my 7 DPO dip my bbt just keeps going up. For reference my typical temp is around 97.70ish, and my typical increase goes to 98.10ish. Since the dip it went to 98.54 then this morning was 98.70. I’m aware not to get my hopes up until the missed period, trust me I’ve spent months doing it. BUUUUUT, is this common for pregnant women?