so scared

I'll try to make this as short as possible.  I went to my OB this past Friday because of horrible migraines.  I had a pretty good idea of how far along I am because I tracked my periods and used opk's.  According to all that I was 6 weeks along.  I informed the OB that I had been having very light peachy-brown discharge on and off the whole time as well as very light cramping since I found out.  The OB did an US and could only find a sac.  He informed me that I was either not as far along as I thought or the fetus is not developing and I will miscarry.  Yesterday I had more bleeding that was more reddish in color and a bit more although not enough to wear a pad only occasionally when I wiped or had a bm.  I had a tiny clot about the size of pencil lead and nothing since.  The spotting does not happen every time I wipe just occasionally.  All last night and today I have had nothing.  The OB took blood but I can't help but feel as though I'm losing my baby.  Some forums are saying this can be normal while others say it's an impending miscarriage. I'm just so nervous Bc of the spotting and the US results.  Has anyone else experienced anything like this?  If so, what was the outcome?  I'm scared to death but trying to stay calm.  Any advice would be greatly appreciated!!