Hi Have Had Unprotected Sex Several Times, Had A Light

Hi have had unprotected sex several times, had a light bleed for 3 days then stopped! Since then I have been given the cerazette pill and had unprotected sex from day 1 of starting the pill. 2 weeks after I started feeling sick constantly suffer with the sinus problems I had with my previous pregnancy back ache and had brown thick almost tissue consistency I did do a home pregnancy test which said negative, I am concerned as I've been on this pill before and no side effects, also the only time I've suffered any of the symptoms other than the brown yuk is during pregnancy! Can you advise me of what it might be please