“How does breastfeeding affect your body?”

Breast feeding helps you lose weight much faster after giving birth.

Affects you in mostly good ways. Right after delivery it helps contract the uterus and reduce uterine bleeding. It will suppress ovulation and provide temporary birth control (must be regularly feeding), quicker weight loss. It does require extra calories and calcium so if you don’t supplement with calcium rich food and vitamins you will lose some bone density.
Other good things are bonding time with baby and better immunity for baby.

Typically it will aid in weight loss and overall has many benefits both short and long term. While nursing, your estrogen levels are low (that's why you may not have any menses), and this low estrogen level may contribute to pain with intercourse due to the vagina not stretching or lubricating normally.