Opinions?

So, i have been TTC since July. I was on regular birth control for maybe 6 or so months and I have had pretty regular periods since, about 30 or so days apart. I haven't had any luck but it always came. However, on Feb 14th i had sex with my boyfriend & there was a very very little amount of blood when i wiped (not enough to even get on the pantiliner) i assumed i was starting my period, but it never came. I have taken tests and they've all been negative :( but I don't understand why my period is so late? & i really assumed that the blood on the 14th was implantation. My boyfriend and I both really got our hopes up, is it possible i may still be pregnant and my HCG levels just aren't up yet? Its been 6 days or so since the presumed implantation, also dont knkw when i ovulated, i track it but honestly have slacked this month.