6 months ttc!

We are 6 months into ttc our first! Although I been tracking my cycle for much longer and quite familiar with all the bodily cues. My period is currently 6 days overdue (coming upto a 40 day cycle) which is very uncommon for me!! I took a test on day 1 and 2 of my missed period with unfortunately negative results :( Am now holding out a bit longer to test again and visiting the Doc next week! Just very anxious every day until I test again. My cervix is high, discharge is whitish and alot more than usual, no period cramping but some minor back pain. I am looking for any advice and what to do and when test.