confused over how far gone I am

My periods have been irregular the last few months and I can’t remember exactly when my last period was due it was beginning of June time but can’t remember what date it started, I went for a abdominal scan 12 days ago and nothing was seen on the scan so they rearranged for me to come back a week later and on Monday I had my second abdominal scan and this scan shown the gestational sac, I know abdominal scans don’t show as much as vaginal scans, but if the gestational sac has become visible within the last 2 weeks how far gone does that make me? And when should I expect to see the yolk sac/fetal pole?