It means the ammonia in your urine mixed with the bleach and caused a chemical reaction. I'm sorry, but it's not an accurate way to test for pregnancy. A shop-bought urine pregnancy test picks up trace levels of the hCG hormone in your urine - this hormone is secreted by the placenta shortly after fertilization - a proper HPT or blood test is really the only accurate way to test for pregnancy x
Just sounds like any normal chemical reaction to me.. i think you should buy a proper test