Help ease my worries?

This is my 4th pregnancy, my husband and I had sex this morning... by lunch I had spotting, called my doctor and they said my cervix was soft and it's normal... by dinner I wiped and had a small light brown mucous tissue (like a long stretchy booger), like a plug or part of my lining.... my husband is terrified he hurt the baby. Is there some normalcy to this or should I be worried!?