MIL’s Advice

I’m 20 days late and am on the mini pill. i’ve been on the mini pill for a year and was on the regular pill for 3 years prior to that. i was two days late getting my new package and honestly didn’t think much of it bc it’s not the first time it’s happened. About 5 days ago i took a test and it was negative. My MIL is set on thinking that i’m actually pregnant and should retest because of all the nausea and how i missed my period. I guess all in all, should i wait till i should have gotten my next period to test again or just write it off as stress because of my negative previous test. Usually at 15 days late there would be enough HGC to show up on a test right? Personally I don’t think i’m pregnant but I don’t have anyone else to talk ab this with and get a second opinion.