Help me, I’m confused

Hi everyone! I have irregular periods. And I don’t know my ovulation day. My cycle length up to today is 70th day. I checked my BBT. Considering with the BBT I think This is my 5th DPO. I have some symptoms like nausea, mild headache, little backache from 1st DPO. Can someone tell is this pregnancy symptoms or any other? I’m confused