Should i get sterilized?

i am 24 and i have 3 wonderfull sons i have always wanted 4 children however now that my last son is 19 months old and is starting to grow up i have mixed feelings and i think i only want another baby as a baby if that makes sense i dont think i would like to have another child i think the reason i keep having them is because im worried about what i will do when they are grown up in which case i would be going on forever having babies i always said i would get sterilized after no 4 but now im aware of how i feel im wondering should i have it now instead of having another baby im sorry this all sounds muddled but my head is swimming with thoughts of do i dont i (want another baby) its like i know i want a baby but is it just for the baby part im not sure i want to do the potty trining etc etc all over again grrrr i dunt know any advice welcome although please dont be harsh on me im so muddled at moment thank u x