I had a miscarriage a little over 2 weeks ago and after I stopped bleeding me and my boyfriend had unprotected sex and now I'm experiencing breast soreness nausea wanting to eat everything in sight I went to my dr I gave a positive pregnancy test but I have to go back on Thursday to take another one could I have gotten pregnant so soon

Yes, it's possible.
It's also possible that your hormone levels are still high from your miscarriage.

The second pregnancy test is the best way to determine if it's just your hormones still being out of wack or if you're actually pregnant.

I'm surprised your Doctor didn't caution you against intercourse for a period.

And, yes, you could be pregnant.