So many decisions....

So it's been a long 2 1/2 years of ttc, a miscarriage and more ttc. Since my mc in June of 2014 I have not been able to get pregnant. I have recently been to a fertility clinic. My husband has good sperm (no problems there), I have textbook perfect cycles, I ovulate every month (checked with bloodwork), my periods are of normal length and so on. Today I had a hysterosalpingogram (HSG) to check the latency of my tubes. I've also done 6 months of clomid. My tubes today were clear. So my OB offered me either IUI or letrozole. I don't know what to do? I don't want to want any longer but I don't know what to do either!