Hello Worriedmama3 and thanks for posting, 

I can appreciate that unexplained bleeding can seem alarming, but I don't think you need to panic about it - most likely nothing serious is the matter, however, you need to let your GP know to be on the safe side. Unfortunately, no one here on Cancer Chat can tell you for sure what caused it. 

The NHS website explains why bleeding after sex can occur at this link. 

Cervical screening smear tests look for a virus called HPV which is linked to abnormal cell changes and cancer on the cervix. (The idea of screening is to detect abnormal cell changes which when necessary can be treated before they ever develop into cancer).  Assuming that no HPV was found, this would make cervical cancer a very unlikely explanation for this bleeding so try not to fret about it, but do get in touch with your GP as they are in the best position to be able to put your mind at rest.

Anxiety about health is a very challenging problem to cope with. It might help to take a look at what the NHS website says about it here and perhaps follow the links about relaxation exercises. 

Give us a ring if you want to talk anything over. Our number is Freephone 0808 800 4040 and we are available weekdays 9-5. 

Best wishes,

Julia