dr doesn't know how far along I am

I'm pregnant after almost 8 years of trying. I went to dr for something totally different and she comes and tells me I'm pregnant. great! but she doesn't know how far along I am this was Monday. I told her my last period was April 10th and she said that would make me super early. so I got blood drawn Monday and Wednesday got my results and they said my levels are rising consistently with pregnancy. but she would have to do a ultrasound to see how far along I am. has anyone ever experienced this? she also asked was my Last period normal and I said I believe so.