Unexpected DNA result
A lady I do not know shows up as my first cousin linked by DNA. She has been in touch and told me that either my father is not my birth father and that one of her father's brothers must be my father. This is a terrible shock to me. Is it possible that my mother's father was not her birth father. All the older generation are now dead and so we cannot ask anyone.
That must have been a shock. So sorry a stranger told you this information. Below you can find ways to get help.1
I'm sorry you have had this experience. It is not clear from your posting if you, yourself, have taken a DNA test and/or whether you have associated your DNA results with a family tree on a particular DNA testing site.
Whatever the results of DNA testing, and whatever the claims this other person is making, those results should be "proved" out by careful research of the "paper" trail your ancestors may have left. The paper trail may include birth, marriage and death records, census records, listings in directories, personal histories and any other documentation for a person's life.
In addition to the FamilySearch articles @DebDT posted, here is a link to Ancestry.com's support article about what to do with unexpected DNA results:
My family and I found the DNApainter tool very helpful in considering the odds that my grandmother's parents were "A" and "B." https://dnapainter.com/tools/probability.
In our case, we did not know who our grandmother's biological parents were, but when we discovered through DNA testing the most probable individuals it was still somewhat of a "shock" and unsettling to a certain degree.
Wishing you the best as you work through this issue.0