help?

So I recently got on birth control and my doctor said there shouldn't be any change in my period schedule, I'm supposed to get my period this week sometime, but I feel like it's going to be late, hopefully... so on the 11th of April was my last period, and I had sex the 15th and took the morning after pill the 16th, and I got some bleeding on the 21st of April. I got on birth control on the 25th of April.