This might help -
IgM antibodies develop when an infection is new, really generally speaking. Typically, they wane as IgG antibodies develop, and this can vary a bit from infection to infection. IgM antibodies are your body's first protection against an antigen.
IgG antibodies then develop, and this varies from infection to infection, and from person to person. This is what remains for a certain period of tiime (again, varies from infection to infection - covid antibodies don't remain forever, but something like herpes antibodies remain for life, as that's a lifelong infection).
Covid can leave organ damage, mood issues, fatigue issues, and we still don't know the reasons for all of it yet.
Have you seen your doctor? You can sit and wonder and ask all the questions, but you could also have something else going on, too, and need to get checked out.