What does it mean when you have sharp pains on your side and in the middle of your chest it usually happens frequently but not everyday?

It means: Your body is talking to you! Listen & take good notes. When does it start/stop? Where does it go? What makes it better/worse? How long does it last? Medication helps/worsens? 
If you think it is something you eat/drink/do stop it & see. If better, go back again & retest until u r convinced it is something u should stop. Then stop it. Discuss with Drs.& u all will figure it out