Hi there
If you've done a home test and it's positive, you are pregnant- these tests give very very few false positives (although false negatives are not uncommon). If you use a digital test (eg Clearblue) it can also tell how pregnant you are (although note that the test dates from date of conception- your Obs will add 2 weeks to this as they date from date of last missed period, so if clearblue says "2-3 weeks pregnant" your Obs would say you are 4-5 weeks pregnant).
Anyway, all that aside, you dont need to get the pregnancy "confirmed" as such before you go to see your Obs. Just pick an Obs of your choice and make an appointment for when you're about 8 weeks from date of last period. This is a good time for 2 reasons- 1. If you're delivering in a private hospital, you need to reserve your place at 9 wks (your Obs will do this for you) 2. At 8 weeks they will be able to detect a heartbeat so give you an early indication of viability. I actually went at 6 weeks, which was fine- she scanned me and confirmed that I was pregnant, but I could easily have waited a few more weeks and saved myself $1000.