Online safety
What if someone sends me explicit photos?
You do not have to accept them, keep them, look at them, or feel guilty about what you do next. In many places there are legal routes to have such images removed, and in some places sending them is a criminal offence. If someone is pressuring you, that is a safeguarding issue, not a you-problem.
What this does and does not tell you
This is general information, not a diagnosis. Only a clinician can examine you, take your history and run tests. The same symptom has different causes in different people.
If something is sudden, severe, or getting worse quickly, get medical advice rather than reading on.