And if you still get a negative say a week after your period is due but get a negative...see your health care provider for a blood test. Pregnancies after a tubal tend to be ectopic and the earlier it is detected the better
Testing early is not always reliable. However, tests taken on the day your period is due, or within a day or two after are very reliable now. Even the least sensitive of them pick up HCG levels of 100 or less, so there is no way you would have to wait until 3 months for an accurate test these days. Wait until the day your period is due, then try again using first morning urine and a more sensitive test. My favorite is the First Response brand. I will say though that if you had your tubes tied, although possible, it is not very likely. It does happen though. Good luck to you.