Mili bc

I was on Estrella birth control for a about a year. I switched to a different obgyn. They gave me mili birth control. I'm 99% sure it's just a generic of Estrella. I just finished my 2nd month on it started 3rd 2 days ago. Last month my period was 4 days late. I started again 14 days later. I've been bleeding for 11 days now. Its not like a normal period it's spotting to light. On and off. Is this normal? I read it's a side effect of starting mili but if it's just a generic of Estrella would I still get new side effects? I'm not sure if I need to make an appointment or wait. Anybody experience this?