Should I??

Well I live with my fiancé for 6months already. He is 10 years older than me, he was married before but not kids. last night we were talking about kids and I asked him if he wanted kids soon and his face change completely it was strange because I feel like he was embarrassed or sad it’s just hard to explain. I know his ex wife didn’t have kids with him because she was in school and was in birth control for a long time and when they tried she had three miscarriages, but as far as I know she is already married and have a baby.... But back to my fiancé, last night he started crying and started saying that he thinks he can’t have a babies and I feel like he thinks I’m going to leave him because he knows I love kids. Now my question is if is too selfish of me asking him to both go and get tested for fertility???