It isn't likely but it's not impossible either. You can theoretically get pregnant from intercourse at any time, it depends on when you ovulate.
"Normally" women ovulate on Day 14 of their cycle (Day 1 is the first day of the period). However, some women ovulate earlier and some later and it can vary from cycle to cycle (if you are irregular, your ovulation is probably irregular also. Usually, the period begins 14 days after ovulation).
Sperm can survive in your reproductive tract for 5 days or so...so if you ovulate early it is possible those sperm could still be there to fertilize the egg.
Best thing to do if you do not want to get pregnant is to use protection. If you don't feel comfortable using protection, you can try tracking your cycles using your basal body temperature, cervical mucus and an ovulation predictor kit. You then avoid intercourse when you are likely to be fertile. This method is not as effective as condoms a diaphragm or the birth control pill/shot or IUD, but it is more effective than the pull out method.
If you cannot afford to see your health care provider for birth control, there are programs to help you. This is a link to the state family planning program in your area http://www.doh.state.fl.us/family/famplan/index.html You can also go through Planned Parenthood or possibly your County Health Department.
If you ovulate soon after, you have a 20-25% chance--the standard any other couple has. Are you trying to get pregnant? If not, it would be wise for you to invest in birth control and use condoms. There is never a safe time for unprotected sex.