CD51 18 days late

Hi guys getting really frustrated now 🥹 I came off BC ( patch ) last year August and I have had regular cycles since I was supposed to get my period around 18/20th of February I only got brown spotting when I wiped and nothing since I’m now 17/18 days late still no sign of AF and still getting BFN on strip tests.

I went to the gp and he said to wait until I miss my second period … he also claimed that urine tests were better than blood tests lol but I am not sure about that….

I am still experiencing cramping in my left ovary/ Pelvis , lower back pain and nausea on and off. This is all new to me as I’ve been on birth control since 2016. I am currently 25

So I am not sure what to do now … any advice ?