Does birth control cause irregular periods?

I have been on birth control pills for about a year and a half now. After I ran out and had my period in the middle of March I didn’t have the money to get my next refill so I was off the birth control for about 3 weeks. I am back on it now. I took the first pill from the pack yesterday. My question is, my period is projected to start in 2 days. Now that I started taking the medicine again, should I still expect to have my period or is taking the medicine for 3 days enough to get it into my system and stop the period from coming this month?