What's going on here?

So my period ended on the 27th, had sex on Sunday the 5th without protection (which apparently was my most fertile day).  Last night I had some uncomfortable cramps and couldn't really sleep. Got up to go to the bathroom and got a 'whoosh' of clear liquid when I stood up... Like I peed my pants..  Then this morning, feeling better, got another whoosh but a lot more and was pink with a little bit of, I dunno, veiny looking blood in one spot.  This hasn't happened before. Any ideas? Could this be implantation spotting?