One cycle of superovulation
with IUI doesn't give 100% pregnancy rate
. Also with the follicle size you described, after injection of hCG
, there is very rare chance of ovulation failure. Also menstrual like cramps doesn't indicate failure of treatment (Not being pregnant). Pregnancy is still a possibility. You can just wait for 2-3 more days & if you don't have periods, you can do pregnancy test.