Irregular period this month, late last month, what's wrong?

I am a 23 year old mother of 3 boys. Since having my last child, my period became normal and regular. I could tell when I would start each month and I knew how the cycle would go. Last month I was late by a week. I was worried because I had my tubes clamped after my last child was born. When I started, even though late, it was a regular cycle. I would start and the bleeding be a little heavy, then I am on for 3 days, off for half a day, and on for half a day. After that I would be off until the next month. This month, I was 3 days late. What made it odd was that I spotted, then started the next morning. The last time I spotted, besides being pregnant with my kids, was back when I was in 10th grade in high school. The bleeding was very light, as it has been since I started on Saturday morning. This time, I bled for 2 days exactly, and now when I go to the bathroom, I am barely bleeding. It worries me a lot. Since I had my tubes clamped, I have been having major cramps when I am not on my period. I don't know what is going on, but I'm a little worried about it all. I was told there is a possibility that the clamps could have come undone. I need advice on what it could possibly be that is making my period be irregular this month and what I can do.