Is that even possible??!

I'm posting anonymously because I know people are going to be rude about this one. Okay here it goes......I just found out that I am pregnant. I have only had sex with one man ,one! I called to tell him the news and this is the response I got. He told me that it is impossible because he had a sex change and used to be a woman. Everything looked and felt normal. I honestly only slept with him and I am for sure pregnant.  had it confirmed with a blood test today. Is this even possible or is he may be lying to me to get out of responsibility??