Hi, J.,
I conceived with IVF when I was 37. All in all, we had 4 IVF cycles spread out over a year or a little more. I had an ectopic pregnancy with the 2nd try, and after that one, I took a couple cycles off to recover (physically and emotionally). The 3rd attempt was the most depressing because we only produced one embryo, although it was considered a "good" one (the other two tries, we had produced only two embryos, also considered "good"). And I didn't get pregnant.
After the 3rd try, I took off another cycle because it was the holidays. At that point, my doctor also made some adjustments to the protocol, switching me to different drugs. I had been using a combination of Follistim and Repronex, and he switched me to Gonal-F and Menopur. For that cycle, I got three good quality embryos (a very exciting improvement!), and became pregnant with my now-2-year-old twin daughters.
I had pretty much decided that our 4th attempt would be our last no matter what happened, because the whole experience is so draining (physically, emotionally, financially, etc.). We consider ourselves extremely lucky.
If your doctor hasn't discussed switching drugs, you might talk about that with him or her. My doctor said it shouldn't make a difference, and I can't say that the different drugs were what brought our success. But there's probably no harm in switching and it could help. Also, because it is such an emotionally difficult process, consider finding a counselor to talk to who specializes in fertility issues. The clinic I used had one on staff who came in one day a week, and it was enormously helpful to talk to her.
Good luck and take care,
A.