What Causes Brown Spotting During Menstruation?

Hello there, I m 24 and I got my last period on 31 Jan. I m trying to conceive for past few months but every time it comes with brown discharge and finally after 2 or 3 days it turns to red color. The same thing is happening now also. Yesterday I start to spot brown discharge which is not heavy at all and while on wiping it appear as beige color or it is reddish brown in color. But on pad it is just dark brown in color. I am so wondering what is wrong with me?