Negative OPKs

My husband and I have been ttc for a little over a year now. I've been to the Dr for blood work (just the first step to seeing if anything is wrong) and so far everything has come back normal. My Dr thinks that since my cycles are pretty regular, that I am ovulating but this is my second month using OPKs and I always get negatives. Is anyone else in the same boat? Or have you been there before and have any advice? This is so frustrating!