blood clots/levlen

hi,

i've been taking levlen for almost 3 weeks now and i just discover a blood clot on my right knee.
Could this be a result from the pills? I was asked by the doctor if i or members of my family have had a history of blood clots
and although its rare, blood clots (resulting from the pill) can be severe and that i should stop taking it.
But this was before i was prescribed with the pills.
Is the blood clot severe and should i continue taking the contraception?

Thanks.