I'm 33weeks pregnant and I expierienced my first contraction last night since then my back has been hurting really bad plus my belly?

Exam needed. Labor is a combination of contractions and a change in the cervix. An exam is needed to know if it is occurring so a woman should notify and go to her OB or labor and delivery. This is especially important if not full-term.
Time contractions. It is normal to have some preparatory contractions later in the third trimester of pregnancy, however it is not normal to have regular painful contractions earler than 1-3 weeks before your due date. I would time the contractions you feel and seek medical attention if they come every 5 minutes or more frequently for 30 minutes or more - as this could be preterm labor.