If my memory serves me correctly, I have heard of a little bit of spotting during the Clomid cycle. Just make sure you keep track of it and tell the Dr.
What OPK are you using? You have to be somewhat careful with them. There are many people who find them unreliable. I hated them because it seemed to intensify the whole process. Waiting for that stupid line to show up. Drove me nuts.
I don't understand why they have you doing the opk then they will give you a trigger shot. But I can tell you about the scan (u/s) They do it vaginally so they can see how many follicles you have on each ovary and if the lining of your uterus is ready/thick enough. It's amazing what they can tell you.
I hope this helped a bit. Let us know if you have any more questions. I look forward to getting to know you.
Love,
Rhonda