I have reg mthly cycles therefore im fertile says doc. man was tested for his sperm and his is good. any idea?

Went to dr to try and get prego, dr says since i have mthly menstral cycle like clockwork that i am fertile. We tested my mans sperm and his is good. Next dr suggest i get a HSG, whick is expensive, any helpful tips i can try before spending big money on this HSG procedure, (hsg= radiology test to shoot dye inside me to see if my tubes are blocked)