You need three years of project experience (plus a bachelor's degree) in order to apply for the PMP exam. Additionally, you must have 4500 hours of leading/directing project work. It sounds like you have 1.5 years of full time project experience, plus 2 years of part time experience while you were going to school. That fulfills the 36 month requirement. However you need to add up your project management hours to see if you have achieved the 4500 hour requirement for leading/directing. If you fall short in this metric, you'll simply need to wait and gain more experience before you apply for the exam.