7 weeks cervix closed but no sac??

I found out I was pregnant about two weeks ago- had a very faint line on a HCG cheapy test and then a week later a very clear positive on a clearBlue test (Jan 26) I called my OBGYN and based on my last period start (dec 13) they said I could be about 7 weeks along (yesterday feb 1). However, yesterday around 3 pm I started having cramps that were different more painful from the normal cramps I had been experiencing(light and came in waves throughout the day). Around 3:15 pm I went to the rr and there was blood in my panties. It was dark red with some clots in it. I called my my OBGYN and they told me to wear a pad and monitor my bleeding and if I fill a pad in an hour or two to go to the er- well that never happened. The cramps were easily a 5-6 on a scale of 10. To me that means they were bearable but they did hurt. Around 7 I was experiencing so much pain I had my bf drive me home so I could just lay down. These cramps were like a 10 on the scale. But still not a lot of blood. It wasn't light but it wasn't heavy- but during this time there was next to none only a little bit of tissue. This pain lasted for about 30 minutes then subsided back down to a 2-3 for the rest of the night and the bleeding got lighter and lighter. 

This morning I went to the dr and they looked at my cervix and said it was still closed and the bleeding could be cause we had had sex(Jan 31) and my cervix is just sensitive cause she said even when they swabbed it bled some. She also said my uterus felt like what it should for how far along they thought I was. She sent me for blood work and a ultrasound. During the ultrasound they couldn't find the gestational sac and said it could be cause I'm not as far along as we think??

Now I have to play this waiting game and I just want to know if anyone else has experience this and what the outcomes where?? I'm so worried that I might have passed the sac :( especially since I've seen photos of people's ultrasounds at 4 and 5 weeks and there was still a visible sac.