Tanya: See what the doctor says first and consider solids because some babies are just fussy and introducing solids at this age is fine and dandy. Jude gobbles down his rice cereal in the morning.
You should know that the choice to start with formula is a difficult and painful choice that will keep you second guessing yourself for a long time. However, you will be able to continue breastfeeding for a couple more months with formula supplemented, so it won't be an instant end to breastfeeding (this is, of course, based on my experience).
Jude is now fully formula fed, but he is always content and happy after his feeds now (he never used to be when I BF him) and I've finally accepted the situation after months and months of guilt and frustration and an inability to completely let go, despite how stressful and soul-destroying breast feeding became for me.
But breastfed babies do dramatically decrease their weight gain from 4 months on, so there's a good chance you have nothing to worry about. The growth charts are based on formula fed babies, so ignore them if you're breastfeeding and listen to the professionals.
