Your university would normally have a policy document on this subject and you might try contacting the registrar's office and asking if they have one. Don't go into details why with them.
For reference this is from Swansea's Revocation Of Awards document :
Revocation of Award
The University may, on the recommendation of the Senate, revoke an award and all privileges connected therewith, having determined that there is good cause to do so. This may include where a person
has after investigation, been found to have obtained an award by fraud or deception, including unfair practice;
obtained an award due to an administrative error or irregularities in the conduct of the Examining Board.
There's an explanation of the procedures required as well on that linked page.
Recently, I learnt that I may be facing yet another confusion with my department (regarding my choosing to publish dissertation findings with a certain professor and not including the department head).
There's a possibility this could be construed as academic misconduct, although the details would be important in making that assessment.
I think your best bet is simply to see what happens, rather than anticipating the worst. Again there should be a very detailed policy document on this available from the university.
I think if it's a case of genuine mistake it's very unlikely much would happen at all, but you'd probably need to have committed some major infraction (misrepresenting a substantial body of work as your own would be typical) to suffer a loss of the whole award.
If at all possible try and discuss the issue with the people involved and ask for advice on how to rectify any error by e.g. contacting the publishers and seeking to make a correction.
I don’t think I’ll have the strength to act, if something like that happens. I’ll want to give up on everything.
Your comments make you sound somewhat depressed. I suspect you're suffering somewhat from a difficult process qualifying and may have actual clinical depression. You might consult a GP about this, rather than anything else. Final stages of qualification can do this to people - it's very stressful.