Question about Clomid and late AF

This is the situation: I started my first round of Clomid 50mg (from day 1 to 5 of cycle). My period works like a little clock...Every 26 days it is there! Right now, my period is 5 days late. One week ago I had mild cramps for 4 days in a row (like I have every month right before my period, but no sign of period. And now I only have some light cramps that comes and goes and my breasts are sore. I took one home pregnancy test today (the early ones) and it came out negative...I was told by my doctor that my chances of getting pregnant are low, due to my husband's low sperm motility, so I am all confused here. I would love to know your opinion about it. Doctor appointment is only in 3 days, cause we are getting prepared for a IUI. I never had one late period in my life...Could you tell me what you think about my situation please? Thanks, Cris.