HELP!!! Clomid and ultrasound q!!!

Hi ladies! So I just finished my second round clomid day 3-7 100mg and have a day 14 us scheduled if I do not get a positive opk before day 14. Today is day 11 and negative opk.

1. Does anyone know what they will do when they check? I know they are looking for follicles but what should I expect from this drs appt?

2. I’ve heard of ladies getting trigger shots, can anyone with experience tell me when and why they decide to give u trigger hcg shots?

Thank you in advance!!