A positive is usually a positive. What colour was the line? Clear Blue are notorious for giving false negatives - the blue dye tests just aren't as sensitive as the pink dye ones. First Response is the best one to use. Were any of these test taken with first morning urine? If not, then I would advise doing so. First morning urine is the most accurate since you're urine has not been diluted by drinking fluids for hours so it has the highest levels on hCG in it.
Do you have a dollar store near you? Those tests are pretty good as they're the pink dye ones? If not, I would get a First Response and re test with first morning urine tomorrow and see what comes up. If it's positive then you're pregnant and if not, the you possible won't be and got a false answer on the first test.
the thing with home pregnancy tests is you cant really have a false positive as there had to be some hcg in your system that it has picked up. It could possibly be that the first test you used was just that little bit more sensitive than the other 3. Or you could be like me where i took 5 tests in Dec, 1 was positive and 4 neg and it ended up being a chemical pregnancy. I would leave it a week for the hcg to become a lot higher and test again :)