Any idea of what could be going on?

Been ttc. I usually have around 3days-5days of my AF. For the first 2-3 days I am usually very heavy then light to none. However ,I started yesterday morning around 5 am. So today is day 2. First day of period I had really bad menstrual cramps and lower back pain. Woke up this morning feeling amazing no cramps no back pain at all! Usually have to.change my tampon almost every hour. Today I changed one when I got to work and noticed wasn't as heavy as it usually is. And now the one I just changed didn't have any blood at all! Still no cramps or anything. What could be going on ? Has this happened to you? Is it normal ?