The advice given in the 1950's was really wacky and not good for babies. In the 50's some pediatricians recommended juice and solid foods IMMEDIATELY for newborns. And of course breastfeeding was widely condemned. They were wrong.
The World Health Organization and The American Academy of Pediatrics currently recommend 6 months for solid foods.
There are good articles about starting solids here: http://www.kellymom.com
If you are from a family with food allergies, many sources recommend waiting even longer than 6 months, if you do a search for solids at http://www.drjaygordon.com
Basically all those early solids in the past were an experiment on babies. Science has learned since that early solids can lead to food allergies (with symptoms such as rashes, stomach upset, constipation or diarrhea, eczema, asthma, chronic ear infections, etc.) and obesity later on.
I just read an article that found early solids were associated with lower intelligence! The article was about full term babies weighing less than 6 lbs. who didn't have anything but human milk for 6 months had IQ's eleven points higher, than babies who had solids or formula supplements before the age of 6 months. This really surprised me! I guess all those "good fats" in breast milk that build the baby's brain are even more important than I thought.
My dd didn't like solids until 9 months. The she started to love them. She's fine, in fact she's GREAT.
It is exhausting sometimes to adjust to how very, very frequently a 3 month old baby (or older) needs to nurse. But you are doing the absolutely BEST thing for your baby! And frequent nursing is normal and healthy....that's one of the pieces of knowledge we lost as a culture when bottle-feeding became the norm after World War II. There are so many times that a baby will nurse frequently for a while, then slow down, then increase feedings again, over and over. This is normal.