Brown spotting? :(

Lauren • Our little miracle Caroline arrived 1/28/15! Thanks glow!
Hi ladies,
​I'm 14 weeks 1 day. On Tuesday I noticed I had some menstrual like cramps on and off all day...and that night around 7 I had 3 drops of light brown spotting in my underwear. I called my doc and they got me in next morning to check me and baby out. Baby was fine via doppler with the same heart rate it's had all along, and my urine and cervical fluid came back infection free. My cervix is also closed...doc told me everything looked fine and only to come back if I see red blood. Since then I've had the brown spotting everyday, and the menstrual like cramps...I'm just worried as everything I've read said this can be a threatened miscarriage. If so, why didn't my doc do an u/s? Should I call back on Monday and insist on one? Has anyone experienced this and delivered a healthy baby? I had no spotting in the first trimester at all!