Advice plz (im worryed about my gf )?

my gf as had sex before i have as well !!!
and last night we decied to sleep togethere for the 1st time xx
n i the moring we found trace ov blood on the sheet n she was bleeding slightly...
we was both checked out for stds before we sleept together !!
we both hadnt had sex since september !!

wot could hav caused her to bleed !!Advice plz (im worryed about my gf )?
could have been left over blood from her period yes
most cases if she isnt in pain or you didnt hurt or rip or tare her thats most likley the cause
That use to happen to me.I ended up finding out I had Uterine cancer so please have her get checked for a papaloma virus!(Not a Std)
women sometimes have breaks in the bleeding when they are on their periods, it could be due to that. there is also the possibility that, and i'm not trying to inflat your ego here, you may just be too big for her or the sex was too rough or dry. if you both have been tested for std's and came back negative, then i wouldn't attribute the bleeding to that.