Hugs honey..

The same thing happened to me. I KNEW I was 6 weeks. I went for a scan as I had been bleeding and they said I was only about 4.5 weeks and to come back in two weeks. It was impossible for me to be only 4.5 weeks. But I just assumed I was losing bub as I was bleeding and my hcg was low and slow to rise. went back in two weeks and, sure enough, I was suddenly 8 weeks pregnant.
Don't give up hope. I really thought this baby wasn't going to stick around but he's still here.
Good luck babe x