Possible ovulation before HCG trigger

I'm currently taking stims for an IVF egg retrieval. I had an Ultrasound Friday which showed one overly developed folicle and the nurse told me there was a risk of my ovulating naturally but that the doctor wanted me to continue with my meds and she would be watching me closely. I have another US tomorrow and I'm really nervous that this cycle is going to be a bust. 😢. Positive thoughts please!!