Brown one day period?

So me and my hubby have been trying to conceive for a number of months now. Yesterday I started my period(the day I was supposed to), but it was brown and light flow. So I was a little let down once again. But today I woke up and now nothing, not a drop. And that is highly unusual for me, I usually have a very long and heavy period lasting anywhere between 7-9 days! pregnancy tests are coming out negative, but it doesn’t make sense to me. I’ve NEVER had a one day period in my life. Not even a five day unfortunately. Any idea what could be going on?