why am I having such a heavy period?

So I missed my period for like 40 days and yesterday day I got it and it was light and now today it has been really heavy in just the last 4 hours I already had to change my  tampon 3 times! I noticed because on my panty liner it kept leaking out where as if I I had in there too long but I just changed it I'm wondering if it's becaus I'm late that this is the reason why I'm having such a heavy period never had this happen to me before