There are many options that are available to you if you do not have the financial security to buy something that can be expensive, like a pregnancy test.
Most cities and small towns have clinics that administer free home pregnancy test to anybody, whether you are someone who cannot afford a home pregnancy test, to people who can, but would like a professional to administer the test for them and help with reading the results. Popular clinics can include Planned Parenthood, a clinic that has tried to make itself readily available to as many people by having thousands of locations across the United States, to smaller clinics run by your local church or government initiative.
Not only are these clinics free, they offer you a chance to keep your results as confidential as you would want them. In no way will they send you anything through the mail and since it is free there is no links back to credit cards or bank statements. I believe, most clinics will just ask for your name, and not necessarily any other information about you. You cannot get any more confidential than that, unless you actually buy a home pregnancy test.
Also, some clinic might actually offer home pregnancy tests at a very low price (some as low as $1). This is not the same as free home pregnancy test, but will help if you are in financial problems. To find these local clinics either look in your local yellow pages, or the yellow pages online, and give any clinic a call. If they do not offer free pregnancy testing themselves most of the time they can point you in the right direction!