I'm 13 and its be 4 weeks since I get my term. I usually take it surrounded by 3 weeks.?

I'm worried. It never took this long before. Please help out! There's many explanations for irregular period.
Some may be:
1. Frequent large amounts of stress, or spontaneous small amounts as resourcefully.
2. Health; from as small as a cold to as big as a disease or STD.
3. Activity; if you're suddenly very live (whether it be in sports or newly exercise) it will reflect on your time. Sexual activity counts as economically.
4. It depends on how far you are into your period. During the first few years, your extent will be very irregular, but eventually it will steady out.
Stress relievers (pills), smaller number physical activity, more experience near menstruation, and diagnosis for your illness will minister to your period return to typical.
are you sexually active ... except then it might a moment ago be that ur irregular many those are like this