First-you never, ever, never put cereal in a bottle unless it's prescribed by the pediatrician to treat severe reflux. It promotes over-eating and thus begin unhealthy eating habits. This is an extremely outdated practice that is not beneficial to baby.
It's not men making up the guideline to wait 6 months. It has to do with the fact that babies have an open gut. Meaning they have an immature gut system that "studies have shown that an immature gut may allow whole proteins, microbes, pathogens and possibly bits of foods to pass into the bloodstream. It is quite possible that this is a causative factor in developing food allergies and "colic"." (taken from wholesomebabyfood.com)
Here is the complete article. Very eye opening as to why it's important to wait to introduce solids.
http://www.wholesomebabyfood.com/early-solid-food-feeding...
Solids never made a difference with my kids as to sleep (and I never started prior to 6 months).
Sure the baby may be sleeping. It might be related to the fact that he was ready at that time to sleep for longer periods. My daughter slept 5-6 hours at 7 weeks. Or it could be he is sleeping because his little system has been bogged down with cereal that he doesn't need and can't process. This deprives him of the nourishment that he needs. Not an idea I relish for my kids.
I breastfed both my kids exclusively. One nursed till 16 months and the other to 20 months. One didn't sleep thru the night until he was 7 months old. The other was over a year before she consistently slept thru the night.
Getting up to feed our children is part of what we sign on for as mothers. They are tiny and depend on us so heavily for such a short period of time that they deserve to be given the best by us as moms. I don't mean to sound harsh but I've been there done that. My son was a preemie with special needs and I was there for him round the clock until he was 7 months old.