Pcos and negative pregnancy test

Hello ladies so I’m currently 18 days late on my period I have been diagnosed with PCOS when I was 16 I’m currently 21 . I was on the birth control pill but had to stop taking it for neurological issues that had been going on been a month since I’ve been off of it . I’ve started having nausea every morning and it comes and goes through out the day. I have cramping in my lower abdomen and started noticing white discharge more than usual . I’m bloated all the time and feel epigastric discomfort : I feel like I’m constipated .. and i have a hard time sleeping because my lower back bothers me . I took a pregnancy test the ones that you’re suppose to take 6 days before you’re missed period but it was negative . Is it likely that PCOS gives you false negatives ? What do I do ? I don’t feel like myself and I’d appreciate the insight from you ladies 🙂

P.s. I lost 100 lbs due to my pcos and periods seemed to improve I was only on birth control for maybe 4 months .