1st US questions

Rebecca • 28 💗Married an amazing man 10/7/16👰💏 💙 baby #1 was due 7/2018 - ended ectopic 💔

So today I am 6+2 LMP and my husband and I got preggo using ovulation tests so I know I'm 6+2 becaise of when I ovulated. Yesterday at work I got a really sharp cramp on my R side that was shooting down my leg but no bleeding so I was worried maybe ectopic. I went to the doc and she did an US and said that although it doesn't seem ectopic that it's really too early to tell and that I'm not as far along as I think, more like 4 or 5 weeks...... OBVIOUSLY I'm like that's impossible because I know when I ovulated. She didn't really have a solid answer so they decided to draw my blood to make sure my HCG levels are where they re supposed to be and they re going to draw again tomorrow to make sure they're increasing. Has anyone else experienced this???