had sex in april, only scared about precum. took plan b 12 days before my period was due. fast forward, my period came on time after it.. normal length & all. my next period is late by a day.. it's been 37 days since the incident and I tested today which was 26 days from the possible implantation day considering 12 days is the latest. had a quanitative blood test done 10 days after the sex and that also was 10dpo (levels were less than 1) at the time. is a HPT accurate now?