I had a period on the 9th of this month and I started again a week later on the 20th and I want to know what could be going on?

Probably nothing. I would, however, do a pregnancy test and repeat one in about a week to make sure that a window period hasn't missed. The brain-ovary-uterus axis is quite sensitive to a lot of things (e.g. Stress, weight changes, diet changes, etc...). Any one of these things, including a pregnancy, can alter the normal cycle.