I need some opinions!!

I am 10 days late as of today, which is very, very abnormal for me. I’m normally super regular. My last period was the 3 October.

My partner and I had a lot of unprotected sex when we went on holiday last month. We left on the 21 October, got back on the 2 November. We’re sort of trying for a baby but taking a casual approach for now as it’s a very new decision. I haven’t been testing for ovulation or anything like that so I don’t know when I was fertile. A few apps say I should have ovulated on the 19/20 October and we did have sex that day, but he didn’t come inside me.

I’ve taken 4 tests and they’re all very negative. I don’t have a lot of symptoms - I’ve had a headache every day, feeling tired and emotional, some days I’m very hungry and others not at all, but that’s it. Boobs aren’t sore and I don’t feel sick.

I’m really confused as to what could be going on. I had the flu when we came back from holiday, so it’s possible that the travel and illness caused some changes to my cycle, but I wouldn’t have thought that a 6 hour flight to Bali (our third time there) and the flu for a few days could cause this much of a change if I’m not pregnant.

My other thought was that ovulation was delayed, and my partner did come inside me on the 26/29 October, but even then I would have thought a test would show up as positive by now. I’m mostly using First Response manual and used one digital.

Does anyone have any experience with something like this? My next steps are to wait a few more days, take another test and if it’s negative, go to the doctor.

Thanks!