Should I be concerned?

I had the same problem with a low dosage birth control pill. I went for about four years without really getting a period and then my body adjusted to the dosage and i started getting breakthrough bleeding and had to increase the dosage. Have you seen your doctor to get the new prescription for Yasmin? If not, I would and also it would not hurt to take another HPT. Make sure that you are still using condoms during to protects against STDs that the pill will not prevent. YOU have to keep YOU SAFE!