Ladies I need some guidance, advice

My fiancé and I have been together for a year & we are getting ready to have our first baby. He just got me a new car, & were moving into our new home together. He lost his ex girlfriend to a sickness. And her sister texted him on her death anniversary he said he was giving support because apparently he's still grieving as well. But the bad thing that he hid that he spoke to her. I feel completely crushed and cheated. I feel like he still loves his ex whom is dead and he's with me because it's convenient for him. I feel completely heartbroken. I also feel selfish and foolish to feel this way. Keep in mind I'm pregnant as well. I don't know who to reach out to. Will someone please help me with this situation . I feel like a terrible person. :(