Nausea vomiting dizziness back pain and abdomainal cramps but had periods last month is there a chance that i could be still pregnant?

No: The question is vague and not clear how long ago was your last period. If last period is less than 4 weeks ago, it is highly unlikely you have that kind of symtpoms from a pregnancy. If you have history of menstrual migraine, you may get your period pretty soon.

Yes: Yes there is a chance if you had unprotected sex, there is also a chance that you might have a vaginal infection since you've had an unprotected sex.