If you are only putting in 1/3 to 1/2 of the balloon inside, it is impossible that you caused the water to break. It is very common in the end of pregnancy that there is a lot of watery mucous from the cervix that is in the vagina, and sometimes women think this is their amniotic fluid. I suggest you change your underwear, put in a clean pad and see what continues to come out. If it is clear fluid or pink or smells like sperm then see your doctor to check if it is water (amniotic fluid). There is also a lot of sweat now with the heat and women find their underpants always damp. It is normal that sometimes urine leaks in the end of pregnancy as well. It is also possible that since you are already 39 weeks, that coincidentally you are leaking amniotic fluid. Put the pad in and see what happens. I also think that superpharm sells pads to identify amniotic fluid.