How Long Do The Follicles Need To Rupture Normally?

Hello, I got my periods on feb 24. Today(11.3.205) is 15th day.According to Ultrasound, still my follicles are not ruptured. Why it is because? And how long it takes to rupture normally? One of the important, I have three follicles also, Is there anything misleading? What I have to expect now and what should I do Thankyou in Advance.