I am aving funny periods?

i have always ad normal periods but have been trying for a baby for quite a few years and nothing happened docs say i av unexplained infertility and they wont but me on any fertility drugs because i am ovulating fine and they say it might reverse it so they put me on the ivf waiting list.Anyway so i started doing my own enquiries into helping me concieve so i bought some agnus cactus (vitex) since i have been taking it i have had funny periods . has i said b4 i always come on every month normally give a day or two but now my periods are not regular. I had a period on 20th oct then 3rd nov then 18th nov, 5th dec and then i had about half a day of bleeding on the 18th of december and nothing snce i took a pregnancy test on the 11th jan just to c it was bfn my are killin and have been for about 3 wks no utha symptoms really the occasional cramping over the last few days can any one tell me whats going on pease and by the way my s only normally hurt for a few days b4 i come on thanx