I would at least do some reading on what should be happening when you are doing clomid cycles. I just completed my second Clomid cycle last week (well I guess I "completed" it, I'm pregnant! :-D Then after you are more knowledgeable on the standard protocols, I would discuss with your doctor why he isn't following them. You can always ask for more monitoring than they normally do. My OB usually only does a day 3 ultrasound, and does not do further ultrasounds to check your follicles as you approach ovulation. But he was willing to fit me in to do an ultrasound because I was concerned about whether I was really ovulating or not, even with a positive progesterone test.
I was getting only one line on the OPK tests right around the time that I was supposed to ovulate, so I asked my OB/GYN to do an ultrasound to see what my follicles looked like close to ovulation to get a bit more information on whether or not I was ovulating. When he did, he commented on how many folicular cysts (eggs) I had and the sizes of many of them. He also stated that due to this, I would not be able to take Clomid the next month, but would have to wait for a month before trying it again. I also a fair amount of pain due to the fact that my ovaries were really in overdrive.
If you have the same reaction to Clomid that I did, it could be dangerous to take Clomid for 3 cycles with no monitoring. I would at a minimum recommend a progesterone test at 7 dpo (my OB/GYN did these), and an ultrasound on day 3 of your third cycle if not on the second as well. Otherwise you are putting yourself at risk for problems, and potentially for multiples.
I'm a little concerned that I may be carrying multiples. I don't know that I am more likely to be, but it makes sense to me that if you have too many follicles developing you are more likely to ovulate more than one egg. I am seeing a RE on Monday and will be asking some questions about that as well as other things then. I also hope that they will be able to tell me at what point we will be able to tell for certain if this is a singleton pregnancy or multiples. I would be really concerned if I am pregnant with triplets or greater. I have friends with triplets and quads and the risks for both the mother and babies are so much greater.
Also, it is suggested by most doctors that you should only undergo a limited number of Clomid cycles per year or in your lifetime. So as wannabe pointed out, you are potentially "wasting" three of your tries if you don't get the proper monitoring to be sure that you are ovulating and everything is going well. Some women don't ovulate at all on 100 mg of clomid.
If you don't have any of the infertility books yet, I would be glad to give you some recommendations of several I found helpful. I checked out a rather large selection at my local library! :-)
Btw, I was also started on 100 mg of Clomid. I did not bother to ask why. I personally figured it wasn't that big of a deal. Maybe when I go back to my OB for my prenatal care I will ask about it out of curiousity. I did use the same OB/GYNs at the end of my pregnancy with my dd 4 1/2 years ago and since then though. So I feel pretty comfortable in their medical decisions in general. In fact, this particular practice is highly recommended by many people in the Los Angeles area because they do allow you to labor in a tub in the hospital. Several doulas and my Bradley teacher told us about how great these OBs are; you have the benefits of a hospital birth where if there are any problems you can deal with them immediately, but they are also very low-tech unless there is a REAL problem and they don't push interventions on their patients. :-) (Unlike the OB that I saw previously that said that I would have to be monitored continuously for most of my labor. ugh!)