No need to worry about the implantation bleeding, as it is actually not very common. Best of luck! I hope you get a positive test in two days!!!
The bursting into tears is more likely to be from the hormones you are on than to be a definite signal of pregnancy. You won't necesarily get any implantation signal, such as bleeding. Heartburn will have nothing to do with pregnancy at this point (heartburn from pregnancy comes on only when your stomach is pushed upwards in your body by the growing baby) but it might have something to do with the hormones you are on. Ditto being hot. None of this is a sure sign, but you still could be pregnant since you did an embryo transfer 12 days ago. Good luck in 2 days!!!!