hi guys... trying and waitin 13 yrs to get pregnant

nothing happening.. just a question! my periods are all over the place.. i never have a set date for them. this make trying to convieve on the rite day very hard

i had my period on the 15 of august and finished on the 18-19... then i missed september's period. i had my period on the 10th of this mth and finished on the 14.... can sumone please tell me when i should start testing for ovulation plz :(
does the first day of your period start when u just get a brownis stain ? or when u see blood ? and the last days ?