As you probably already know, having had one ectopic (tubal) pregnancy means that you may be more prone to another. It is good that you are aware of what signs to watch for as indicators of ectopic. Light bleeding such as that which you are experiencing can be one of those, although often bleeding with ectopics is darker. Other signs may be fever, discomfort or pain low in the abdomen or pelvic region, some early pregnancy symptoms (nausea and nipple tenderness), shoulder discomfort, dizziness.

Tubal patency, like many diagnostic indicators of fertility, is not black and white. Rather, there are ranges of patency, depending on several factors: possible adhesions, mild level of infection, poor lubrication or cilia movement, etc. To what degree your remaining tube is patent and for how much longer depends somewhat on any pre-existing reasons that led to your previous ectopic. For example, if the ectopic resulted from an STI (the most common cause of tubal infertility), the possibility exists that any minimally remaining infection could impact the remaining tube.

At any rate, with your history of ectopic and having trouble conceiving, you would be wise to contact your medical practitioner immediately. An ultrasound should be able to determine whether or not an ectopic exists, and it can be treated accordingly, before you lose the other tube.