My nursing toddler also nursed often.
I found I was MUCH happier if I ignored the clock and did not count the number of times my child nursed. It brought peace to my home.
Your feelings of wondering if you caused this are normal in our antibreastfeeding society where only half of moms nurse their newborns and the average weaning age is 6 months. (This is what I've heard, these stats may be wrong.) Here in the West we do not get to see what is NORMAL, the normal range of variation where some two year olds are not interestedin nursing and others are avid nursers. A few generations of formula feeding in the US (my country) have destroyed our support networks and our sense of what is normal.
It is very normal to feel burnt out and ambivalent while nursing toddlers. Two books that address this beautifully are
How Weaning Happens
Mothering Your Nursing Toddler
You wrote that you offer her good nutrition but that does not keep her away from wanting to nurse. Again, our culture tells us human milk loses its value after a few months but this is A cultural attitude and a MYTH and it is NOT based on facts. Mom's milk is very nutritious, has naturally relaxing and pain relieving chemicals in it, and is attached to *******YOU********
who cannot be replaced.
I had an intensely needy child who also nursed often at that age. It was indeed exhausting. I felt lonely, when the other one and two year olds I knew lost interest in nursing. But she DID gradually lose interest (with periods of increased nursing even past 3, during stressful times, transitions, illness, growing etc.)
So to sum up, your child is normal, your feelings are normal, every child is different, and our society is backwards because it thinks breasts are intended for the enjoyment off adult males (and MAYBE tiny infants) when the biology of children suggests a normal time of nursing of about 2 to 7 years.
Not that you MUST nurse for 7 years, not that YOUR child will necessarily want to.......just that all of this is NORMAL.
Take the time to heal from your marriage before you move on with someone else. Make a list of all the qualities you would like in a new partner and then work on growing that way yourself. ~mandib50