I am almost 6 weeks and have brown spotting...

Hey ladies, I am almost 6 weeks pregnant. We tried to get pregnant for well over a year before we were finally successful after taking letrozole. Last night I woke up in the middle of the night to pee like I have been..but this time I noticed I had some uncomfortable cramping. I became very paranoid, text my husband (he works 3rd) he told me to relax and try to go back to sleep, so I did. When I woke up this morning I went to the bathroom and had brown blood. I called my DR, they told me to keep an eye on it and if it got worse to call back. Well it hasn't gotten "worse" but I am still have dark brown spotting when I wipe and this evening after eating my cramps became uncomfortable again. Any one else have a similar experience? I am just scared and a nervous wreck.