Teenage problems?

Hey guys I started my period when I was 12 usually it was very on time and I never used to get cramps,back pain or tender breasts. However now I am 15 and I've noticed that my period came every 32 days for 2 months and now it came on day 24 I don't know if I should be worried or not bare in mind I've been traveling and I was stressed. Btw I know get cramps back pain and sore breasts I don't know if this change in my body is normal