An ectopic pregnancy will always cause problem because of it's complications and terminate itself (abortion). Even abdominal ectopic pregnancy cannot survive for full term and give birth or deliver, as nutrition to fetus will be affected at some stage or the growth of fetus will affect the adjacent organs, ensuing complications. Read here;
It is quite rare. Read some reports;
In the first report you can read the ways, how it can happen.
Since it is quite rare, chance of pregnancy would be very remote. Do not worry about it. Condoms are usually not necessary after total hysterectomy to prevent pregnancy.
Probably pain abdomen would be the most common symptom. The period kind of thing which you get from the cervix, needs to be evaluated by your doctor. One gets periods because of uterus and endometrium shedding. The cervix if giving you bleeding, has to be examined by your gynecologist.
There has only ever been 36 reported cases of ectopic pregnancy after hysterectomy.( as of 2006 anywhere in the world )
Most of these have occurred shortly after surgery - ie there was a fertilized egg in a fallopian tube at the time of surgery.
Therefore your risk of becoming pregnant is less than one in a million.
This would present with - pelvic pain , abdominal distension, vomiting , breast tenderness and sometimes vaginal bleeding.
I hope this helps.