DR. and/ or someone experienced: IUI soon should we BD tonight?

Hello, I tried to speak to a nurse in the office but it was too late. Please let me know your thoughts: Today is CD9, tonight will be 7 nights of Follistim @ 75U.ultrasound this am showed 2 follies at 17 & 18 and then a few others that are smaller, one 13. Estrog. is at 1,242 (Sunday Estrog. was 577). The phonetree (message left for patients with instructions and results)said to do another injection of 75U tonight and come in tomorrow for another u/s. Should we BD tonight? We haven't the last few days so I want to make sure he has new sperm for the IUI but don't want to mess things up and bd too close to IUI. Don't know when they anticpate trigger and how soon after the IUI will occur. THANKS so much!!! :O)