Clomid questions and concerns

how does it work? My periods are very irregular. like super. my OB-GYN said it looks like I have PCOS. He only looked inside me when he said that. Can a ultra sound tell or show me if I have PCOS? I've been trying. To get pregnant for a year now. he also told me to lose weight but it's hard for me to lose it. I'm on a diet now which is working and I love it. But I don't know. I'm concerned that I'm gonna have to have regular periods to be on clomid. Please comment and help me out. I have an appointment on the 30th this month. But I want to call tomorrow. Thanks in advance