Can chasteberry (vitex) help me become pregnant? how do i take it?

I have irregular cycles , sometimes im regular like 35days apart and other times i skip a month but i have never gone longer than 2 months without a period. my husband and i are ttc and its very difficult to figure out when i ovulating if my period varies so much and opks can get expensive. my sister told me about chasteberry (vitex) is suppose to help regulate your period and help u ovulate. so i went out and bought some from the vitiamin shoppe and they said to only take them for 2 weeks cd1-cd14 and stop. until next period starts because it could cause a miscarriage if its in your system when you become pregnant. so i did but how is it gonna help me regulate my cycle and help me ovulate if i only take it for 2 weeks a month?? is this true or can i take it the entire month and stop taking it when i get a + hpt? will it cause me to miscarry ? pls someone help!! has anyone ever taken this and has a successful pregnancy? and how did u take it? i have the 500 mg capsuls. thanks in advance!!