Possible miscarriage

Based on my calculations, I'm a little over 6 weeks pregnant. I had my first dr appt scheduled for 8 week mark, but started spotting light pink and brown on Sunday, just when wiping. Yesterday, I noticed that it was becoming a little heavier and more of a red color. I went to my OBGYN and she did a transvaginal ultra sound. She said she saw a sac, but no embryo which she said was normal since it's still early on. She sent me to get my blood drawn to test my HCG levels and they came back around 430. She said that she wasn't too concerned, but we will have to see how they compare to the results on Saturday to make sure they are increasing appropriately. Last night and so far today, i have noticed the bleeding is more so like when I have my period, and I noticed slight cramping and a small clot. So needless to say my normal anxious self has become much worse. I called and am waiting to hear back to see if I should go back in or wait until i do my second blood draw.

I also haven't had many symptoms thus far, with the exception of sore boobs and fatigue, and I noticed my boobs don't really hurt as much as they have been.

Has anyone experienced anything similar to this and ended up with a viable pregnancy?

Thank you in advance