why would I get a faint line

za
I had my periods 4 days early last mth they come on the 28th march and was lots of clots which lasted 5 days which is normal for me today 11 April I've tested for lh surge but accidentally used my hcg and it's come up faint line does this mean I've had a miscarriage? 
I did do a test hcg early this week and it was negative why would I have a faint now ? Can anyone help me