My case might be a little different. Last April I first went to the RE and had all the bloodwork done. Although I didn't O until cd36!!! my progesterone 7 days later showed a good O.
The next cycle I got pg and unfortunately had a m/c.
I did my first round of Clomid in January... she didn't do any other tests on me, I think becuase of my previous bloodwork and my m/c showed my tubes were open, etc.
Anyway, i was very hesitant to go to Clomid, but after almost a year and a half of TTC I was so sick of those long cycles!! They had normalized a bit after the m/c and I would O on cd19/20 but then in Dec didn't O until cd28... I was just done with all the waiting.
Along w/ the Clomid I had an u/s on cd15 to look at lining thickness and follicle size. At that time they found a suspected polyp... wouldn't have found it w/o the u/s and I'm fine that i didn't have the u/s at the beginning of the cycle.
So... this IS a very personal decision on when you're ready to try it. It was a REALLY big deal to me. Fortunately my s/e consisted of a little heartburn, some minor hot flashes and just one big beautiful follicle. Also, fortunately for us we were successful on the first cycle.
Also... since I've already got a long post... I would definitely have an u/s before O to check things out. In my case I hadn't started my LH surge by cd14 so we did the u/s and trigger. That was a good route, also an u/s when you start your LH surge if it's before cd14 to make sure follicle size and lining are OK. They also measured ovaries, all follicles (I had one dominant and 3 smaller) and anything else they can see on u/s.
I REALLY hope that my experience helps.
Good luck and babydust