Brown spotting on cd 22

So 10 days before af was due to arrive I had very dark brown every time I wiped for about a day and a half. We had sex and then the spotting stopped. I took a cheapy test 2 days ago and it was negative. I’m having pregnancy symptoms and af was due to arrive today but isn’t here. Wondering what the spotting was as I never spot and haven’t had IB with my two previous pregnancies. We would be fine having a 3rd but weren’t “trying”. (We use the pull out method and it has worked for us until we have tried to conceive.) I have another test but was waiting until I actually missed my period. I’m crampy but I usually never have pms symptoms.