looking for help

so today I went for my mid cycle scan since I started clomid this cycle hoping to get the news I could trigger today. instead the doctor tells me there is something in my uterus that wasn't there last week, that I need to get a betahcg(after I took a pregnancy test which was negative) and if that comes back negative I need to get a hydrosonogram now.... has anyone ever had this experience? I'm confused as to why the beta hcg. its cycle day 11 how could I be pregnant... its hard not to worry about there whole situation which my RE tried to stress the fact I don't.

any help or experiences would be amazing