Am I wrong for being this upset ?

So my husband and I have been ttc for about 6 months with no luck . Today I walked into Walmart to buy some pregnancy tests and take all 5 that they had . When I go to ring them up the cashier asks me "So are you trying to have another kid? Or are you just trying to make sure that you're really not pregnant since your son is still small " and she has the audacity to stare at my son who is with me . My response was " My son is 4 years old and his father and I can have another whenever we would like to .. & in this case we are really hoping one of these tests could be the lucky one "....