Can't look at his son anymore

I've been ttc with my oh for 2 years with no luck, 3rd round of clomid and still no luck even though I am ovulating. My oh has a son from a girl he didn't know and slept with one night. I can't do this anymore the endless negative tests, tests, pills and needles is taking too much on my emotional well being and he just keeps saying "we will get there don't worry". Just looking a his little boy breaks my heart, looking at something so beautiful and perfect that another woman can give him so easily and me I'm just a failure of a woman who can't even give him what she has. I'm so confused, angry and hurt and I don't know what to do anymore