How have I not got pregnant ?

I’m not trying to get pregnant, but no necessarily preventing. I feel like something is wrong with me because on several occasions I have had sex close to ovulation and have never ended up being pregnant. I have done this for about 2 years now and have not ended up pregnant. I’m just like how? Is something wrong with me or am I infertile? I always think I’m pregnant every month and it drives me crazy I always have different symptoms before my period and I think it’s because I’m pregnant but I’m not.