i would def buy a first response test - i got my bfp at 11dpo with evening urine using first response and positive came up within 2mins, not very dark but definitely visible. i thentested again the next day at 12dpo with FMU and it was barely visible - had to tilt the test to see the line went to the docs for bloods and they came back showing i'd had a chemical pregnancy (egg was fertilised but did not implant) - my hcg came back at 10 and 3 days later AF started - I hope this isn't the case for you hun