First trimester light bleeding

Did you ever experience it and what was your outcome?  
 
​I went to the hospital on Friday and my hcg levels were taken.. I was told my hormone level is 564 and no gestational sac seen via transvaginal ultrasound. One thing the doctor did mention was that my endotrimium lining is thick so that's a good sign. Still they advised me to remain on pelvic rest until my next appointment. Could I be having a miscarriage? I'm still having spotting with little to no cramps and I have taken four pregnancy tests because I'm afraid that my hcg level is decreasing. The bottom test was taken today.