Fertility Specialist advice

Ma

I’m about to visit a fertility specialist for the first time. Any advice? We have been trying for a year and a half, have always had positive opks, husbands sperm is fine, my tubes are clear...progesterone used to be low but after four rounds of Clomid I was supposedly ovulating every month. Still not pregnant. I’ve always had very normal periods. Anyone experience anything similar? I’m not sure what could be wrong or what is next...