I'm an expert/I know NOTHING!

Why is it that I veer wildly between thinking I know what's best for Abi and how to get her down/keep her down/feed her/placate her, or know she's crying because of hunger/boredom/tiredness and thinking completely the opposite and that I know nothing, and have to ask every other mother I meet their opinion on the matter?? Don't bothering answering that, as it's clearly a rhetorical question, no on second thoughts do let me know your thoughts on the matter....oh I don't know, a month ago five hours sleep seemed a lot, and now for some reason it is nowhere near enough!? Ho hum the ever changing landscape of motherhood, and I've only been at it for fifteen weeks ;-S