What Causes Miscarriages?

i had a baby in 2009 via c section and also had my tubes done.. i use to spot and it always led to pregnancy but had over 10 misscarages which is why i had my tubes done.. i caught mrsa in my c section and in the womb which is now gone but am worried that it may have reconected my tubes as i am late and had middle cycle spotting, ia this possible because the mrsa opened up my c section and my thoughts where that it may have done the same to my tubes, i would of course welcome a pregnancy with open arms but am terrified of the mrsa coming b ack and harming the baby.. nikki