((((Jessica2231))) That is pretty extreme. My cycles changed when I got older back to where they were when I was younger, LOL! I am on the very edge of normal with 21*-28 day cycles (count form the first day of your period) When I complained to my doctor, she did test my thyroid because that could cause shorter cycles. But it was normal, and since this is on the edge of normal we didn't test any further.
There could be many things causing such a short cycle, I don't think weight loss is one (but your doctor could say different)
I hope you find a easy answer. And get relief for those cycles. It must be tiring.
*21 days is the shortest cycle in "normal" according to my doctor.