I think I am overly preoccupied with what my neighbours think of me at the best of times. I live on the third floor (top floor) to give you some context, in a 2 bedroom flat. However this morning my 2 children at about 8.50am were playing chase backwards and forwards across the flat, I was in the kitchen and came into the lounge to ask them to stop and thought I heard a neighbour banging loudly. I couldn't work out whether it was on the wall and therefore the neighbour in the next block or from below. I am now mortified and thinking oh my goodness I bet they all hate having me as a neighbour etc. As neither of them have children as yet and it is generally a quiet block, apart from me 
I'm always worrying about how much noise they make, to the point that I hide noisy toys or party whistles given in party bags. Only run the washing machine in the day and even use subtitles at night so I do not have to turn my old and very rubbish television up too loud.
I live on my own as I'm divorced and the children are almost 3 and age 4. I've actually owned this flat since 2005, so I lived here with my then husband to begin with before children. It is a nice area.
Why am I so preoccupied though about noise, and what should I do if I have pissed a neighbour off? I feel I'm possibly being paranoid now and need some sense talked into me as well as some ideas.