Hi there, I am wondering the same, my ds #2 is 4.5 months, sitting well, very big boy, draining all his bottles and after almost 2.5 months of sleeping through the night has started to wake up hungry...I really cant plough more formula into him, he is getting over 40oz a day as it is. I have decided to give it the rest of this week and see how we go, if he continues waking I may well introduce solids , he will be almost 5 months then. ds 1 was breast fed and waited until he was 6 months but the 2 boys are very different.
A mothers intuition is a very strong thing and I think if you feel your baby needs to start on solids then do it. Recommendations from w.h.o and other groups are just that.....recommendations, you will know what is best for your baby.
When I do start I intend to take things really slowly, am just hoping his wonderful nights sleep is not going to be too disturbed, he is teething like crazy at the moment so I may hold off a little until this little bout of teething eases.
Best of luck whatever you decide xx