Opinions on vaginal ultrasounds

Jessica
Hey Ladies,  
   This is my 5 time conceiving in 15mths... 4 MC.  Last time I was able too see heart beat around 6 week mark.  Two weeks later went back in and no heart beat, baby stopped growing days after ultrasound...I was destroyed.  Now I am 6 weeks 1 day :)
Ok so my question is what are your opinions on vaginal ultrasounds? I've pushed my ultrasound by one week so I'm sure there will be a heartbeat.  Plus will be bigger to see abdominally.  I've talked with a few people who had similar experiences after vaginal US.  Fertility clinic is insisting, I know it's my choice in the end.  TIA ladies