Do speak to your husband about it. Both of you will need to be honest about your feelings. On your end, it's about how his actions affected u and made u feel. On his end, it's about why he's on a dating app. You two have a child on the way, and would need to resolve this for both yours and your child's sake.
Pls talk to your husband, rather than thinking too much by yourself. And come up with some arrangement for intimacy between you two.
Super sad… wishing you strength mummy