yes it is possible, my cousin was pregnant with what she thought was a single child but when she pushed the first twin out the doctor was like OMG there is a second one and she could have fell off the table...so needless to say she gave birth to twin identical girls Baby A weighing 5.6 and Baby B weighing 4.9 she was hiding the whole entire pregnancy,,,we was not prepared for that.
I was 5 weeks when they found my two babies. Ive had 4 ultrasounds after and i think itd be pretty hard to miss another baby but i know it does happen on rare occasions. Good luck!
I think it's pretty rare to miss one in the U/S. It could be that this is your second pregnancy and your uterus remembers. the U/S tech that I had said that many women think that they are bigger the 2nd time because your uterus expands easier and faster after the 1st one.
Same thing happen to me I thought I was having a twins as well I'm way too big compare to my first pregnancy & I also feel same moves & kicks everywhere. But then when I did the u/s found out I have so much amniotic fluid that's y the baby has plenty of room to move around:/... But yeh it's impossible to missed a twin in u/s although I read there's some cases but very rare...yeh best to get another ultrasound u just never know;)