What could this be?

So im a bit confused, me and my boyfriend have been trying for about 6 months now to conceive and haven’t had any luck. my periods usually last anywhere from 5-7 days. My last period was August 21-27, but September 5-7 I bled like I was having a period, even though i wasn’t supposed to have a period until 13 days later. I had creamy discharge and I didn’t have period cramps. I’ve dealt with lower back pain, food cravings, headaches, and severe nausea even two days before bleeding. What could this be?