Long and short cycles

I'm 16 and ever since I started my period just before my 13th birthday, I've always had quite irregular periods especially after my first when it took 6 months for me to get my second. At the moment I get strangely long or short cycles and I don't know if this is normal or not. My shortest has been around 27 and my longest 45 and it can go straight from being extremely short to being extremely long. Is this normal? Is there any sort of diagnosis of what it may be if it isn't?
Thanks for the help❤️