Clomid-days 3-7?....?

so i was put on clomid by my gyn in october, she did a ultrasound while on my period to check 4 follicles, which they did exist i just didn't have a mature one. she prescribed clomid for 3 months and prometrium to induce periods. she told me to take 50mg on days 5-9. i did as she said in october but i didn't have any signs of ovulation(oh which reminds me, she's NOT monitoring me, yes i know, i'm worried about that) anyway, i started my cycle thursday but decided to switch my days to 3-7 to see if it will work, what's the difference does anybody know? what is more likely to bring on ovulation?