It was probably too early to tell
Birth control isn't completely reliable early on in use. You have to be on it for a few months and take it religiously for it to work to it's full ability. Have you missed a period? If you're thinking you're pregnant, and you have a positive pregnancy test.. chances are you're pregnant. You should probably go see a doctor. Stop taking the birth control too.. it can cause miscarriage. Good luck. I hope you get the answers you're looking for.
any pregnancy test can have a false result. you may have not produced enough Hcg for it to show up at that time.
Take another pregnancy test. Lay it flat and don't touch it for 3 minutes. Then look at it. Sometimes the test will give a false positive if moved to early. But no birth control is %100 guarantee. Also if you got on birth control a month ago it might have been too early to test positive on a hpt.
If you've been pregnant a week longer than you've been taking birth control it would have been too early to tell before you went on it. Go and see your doctor and stop taking the BC as it can cause complications