What Causes Spotting With No Regular Period Even After Taking 'meprate'?

Hi, I am 28 yr old married and TTC. 13th august was my last cycle. On 13th sept i went thru pelvic scan and there was no sac found(as my lining was 12mm my gynic suggested to get done UPT as there is chance of pregnancy)and even UPT came out negative. so my doctor gave me meprate to start my period daily 1. After taking 2 tablets i spotted lightly today morning ie on 15th sept but no period came. is it normal? Is there still any chance that i could be pregnant?