I got my bfp at 3.5 weeks so you can be early. But it's hard to say. You will pretty much have to wait till your u/s to find out but don't freak out if they do early u/s and it doesn't show much. Heart beat can be seen around 6-7 weeks. Congrats on your bfp!
Congratulations I had the samething happen to me! I tested got neg still did not feel right and tested a few days later and positive.
Congratulations!.. the same thing happened with the 1st test I done in March, it came up neg, I still didn't have my period a week later and tested again with 2 positives.. it takes a few days for the levels in your urine to go up.. hope this helps :)