I need ADVICE 😔🙄 desperately 😭

Sooo my fiancé is hospitalized & has been since the 21st of July.. it’s a long story & I rather not get into it. Although he’s been fighting for his life and progressively getting better. Although at the beginning of this whole ordeal I seen him texting an ex.. I normally don’t do this but I went through his phone (back in July) he’s been unfaithful prior to all of this happening. At least through the months of Jan-June. I have stood by his side not mentioning what I know due to the seriousness of his health. My pregnant with his 1st child. My question is once he’s home & stable completely, how do I bring up the concern ? I’m completely hurt & I literally battle this EVERYDAY. I’m extremely emotional and secretively depressed but I try my best not to show it. I have two other children whom are very attentive of me & their unborn sibling. So I try to keep a smile on my face as much as possible. I just don’t know how or when exactly I should tell him what I know & how I feel. Pls any suggestions is better than none.