15 days late

Hi ladies I'm needing advice or maybe just some reassurance that I'm not going crazy. I am late 15 days took a pregnancy test yesterday and it was negative. I am regular with my periods and am feeling only very mild twinges and cramps here and there and constant constipation. Could I indeed be pregnant what else could be gng on? I haven't had any stress weight gain or loss. Called my doctor and they asked me to wait until it's been a month so until then I'm in limbo :(