Help me figure this out

Okay so, I’m 8weeks, I was on birth control and got pregnant, excited but unexpected lol i didn’t have a period on my birth control but I did have bleeding in July, the week I usually have a period, I told my dr that that was the first day of my period, I have my first ultrasound on Tuesday!! But I got to thinking, The bleeding, would that be known as implantation bleeding or a period...because I for the life of me am not able to tell my dr when my last period was...I’m so confused

Can they tell if I’m further along (if I am) on an ultrasound? Or how does that work