Elective Gender Determination Ultrasound

So I am anxious, due to 3 previous losses, that even though I am hearing the heartbeat at each appointment, I am worried that there could still be something wrong with the way baby is growing, etc. My fertility specialist told me I should be having weekly ultrasounds (which I do find to be a bit excessive), but still I'm 16 weeks and I've only had 2 ultrasounds, very early on...5 weeks and then again at 8 weeks. My regular OB doctor told me at my last appointment that he wasn't going to do another one until 20 weeks. Have any of you had elective ultrasounds? My hubby is really anxious to find out the gender. Would you trust the gender determination from the ultrasound this early at 16 weeks?