Btw I love my gorgeous nieces and nephews and am so glad I showed them so much love when they were born and as they were growing up- I would adore them all over again if I could!!! I just feel disappointed that my baby won't have that with them.
But your baby hasn't even been born yet, so I don't see how you can decide your family aren't going to love your unborn child. 
Also, you live at a distance from your family members, and they are adults with expensive, older children of their own, so they don't have the relatively endless time and comparatively few outgoings you had in your teens and 20s, so it's unlikely they are going to spend every weekend babysitting, as you did.
You can't expect some kind of equivalent 'payback' for something you did, presumably of your own free will (unless there's a back story you haven't told us about where you were forced to babysit and spend your pocket money on baby clothes) when you were much younger.
I don't see why any of this translates into them buying you car seats and pushchairs. For me, it's much odder that they even offered, unless it was useful handmedowns they had from their own children. Did you misunderstand the offer?
Either way, it's completely unreasonable to start stropping about your family not loving a baby who hasn't yet been born!