I started the pill afew years ago to control symptoms. it does helps the symptoms but my period is very irregular, will it prevent pregnancy still?

The Pill: As long as you take your pill every single day, and don't forget to take it, it should prevent pregnancy with 99% success. However, if you are still experiencing irregular periods even when taking a birth control pill, you should probably see a doctor because there may be something else going on. When you are on a birth control pill, periods should be regular and predictable.