Could I be pregnant?

So my boyfriend and I had had sex a few times. None of the times he cummed -_- But the first time he thought he might of. So we took the plan b pill. This was Febuary. We had like a halfy without a condom the other day and went for less than a minute. But my boyfriend is super worried I might be pregnant. I tried to take a test yesterday and it flashed "pregnant" then it showed a symbol to go to the book. The book said that the test didn't work. What are my chances of being pregnant? I'm going to be 18 soon but can't afford a baby when I got my life ahead of me. HELP!