Brown blood? (Normal or concern?)

To start off the bat: I’m a Virgin so no I’m not pregnant. I’m about to start my period in the next 3-4 days (i have an irregular cycle) and I thought I started today because I felt blood in the morning so I put on a pad. I had cramps all day long and I just looked at my pad and there’s a very very small amount of brown and yellow stained blood. Is this a worry??? I’m 18 btw