What Causes Irregular Menstruation With Tied Fallopian Tubes?

Hi, I had my tubes tied 15 months ago. I have 26 days cycle normally, my entire life. I have gone late before, but I have gone a day or two early more then I ever have gone late. I am on day 29 now. I have had a horrible cycle this month. On day 13 I did one spotting. I think I actually ovulated the day or two before that, but no I do not know for sure. I also want to add that I do not normally spot at all unless it s time for period. I have had cramping mid cycle before though but that is it. Well in summary...day 13-19 I had some form of spotting. Ranging from about 3 days of actual red spotting and the rest being a brown. But during this time, I had two times of what I d call a tiny amount of actual bleeding, or baby gushes of sudden blood. I have miscarried before at 8 weeks, and bleed what seemed like a river. This was not that amount of blood at all to be clear. I just use the word gush meaning, didn t spot all day, just felt a sudden tiny gush of blood. Day 19 was the last day of any form of seeing any spotting or bleeding. I have cramped off and on since day 13. It gets really intense at times and I have just been taking more pills to cover the pill and go on about the day. I have had a rough month, including my oldest child having sudden surgery for her appenditis, so stress levels were definitely high some this last month. I have taken three pregnancy tests. Two were definite negatives, and the third looked really abnormal..was almost like a line, but was white instead of the purple. Very odd looking indeed, but for all I know it was a defective test. They were just the one dollar brand. My question is...how concerned should I be? Is my period just really late? Could it be ectopic?