Hi
I FF both mine (I don't discuss the reasons why, but wanted to reply to you).
Both are fine, and healthy. DC1 is coming up for 9, DC will be 6 soon. DC1 has had very few illnesses, although he does have very mild asthma which was triggered by a severe chest infection. DC is incredibly healthy.
They have had almost no stomach bugs - the last time for DC1 was 3 years ago when he ate some dodgy shellfish on holiday, DC2 last had a tummy bug when she was 2. The chest infection DC1 had has been the only serious illness that either have had.
DC1 has had about 3 days off school in 4 years, DC2 has never had time off school.
Both are clever, DC1 is top of his class for reading, and maths, and wins prizes for his art. DC2 is also great at reading, and maths.
However, that's purely our experience. There is no link between how they were fed, and how they turned out. Your DC will be fine, don't beat yourself up about this (and I know how you feel, I tortured myself over feeding). Focus on giving your child the best that you can; give him/her good quality food once s/he weans; read to him/her; talk to him/her, and be present when you play together. All of these things will help your child grow up confident, and strong.
And, if s/he is ill - don't worry that you fed him/her is to blame. S/he will be the person they are meant to be.
Best wishes