Weird period!

Nia
Sorry if there is TMI coming up but I need some advice.
My peiods are very regular, and been TTC for 21 months. But this month, my period is very strange, I've had no cramps and usually have them, and I usually have a moderate-heavy flow, very red. Again, this month it's extremely light, barely anything and is a very dark brown colour. Is there something wrong??