What can cause different answers on a pregnancy test result?

I took 3 pregnancy tests and two of three came out positive. However, my boyfriend always pulls out, so I don't think this is 100% sure. Im on a versy strict diet and my body fat % is down to about 4 %. I don't think Im pregnant. What other factors could contribute to conflicting results?. I workout really hard everyday, and work out in the sun and I have a vert restricted diet. Any opinions?

Pulling out is not a very effective method of birth control. False positive pregnancy tests are rare. The only way I know a birth control test would turn positive is if you leave it sits for too long after you take it. It must be read within the time limit recommended on the box, or the test is not valid. The a false negative happens quite often as some tests don't detect pregnancy as early as others. Having a low body fat and restricted diet will contribute to missing your period, but not to false negatives.