i dont know whats going on

hi im 31 been ttc for 2 years. my cycles are always between 26 or 27 days between af. i got a positive opk on the 8th of this month, me and dh dtd on the 8th&9th. as of today im on cd29 and no show or signes of af. so why do i keep getting bfn? please advice on what might be going on with me and is it still a chance i could be pregnant?