I just walked in on my husband making out with my sister

Please help... I am absolutely devastated right now. I don't know what to do. I don't even know where to start. My sister(Lisa) lost her husband (Jimmy) 2 years ago in a motorcycle accident. She did not take it well and closed herself off from the world. A year ago, she reached out to us and told us

she was having a hard time adjusting and said that she needed help. I helped her find a good therapist and she has been getting her life back on track. My husband (Rick) felt bad for her and started spending a lot of time with her. For the past 6 months, they have spent more and more time together.

At first I was fine with it because she was finally becoming like my sister again. She started smiling. I was so happy for her, and so was my husband. They started spending more time alone from me which I didn't think much of at first. Then they started spending more and more time alone and I got a little jealous. I told my husband I would like it if we could spend more time together and that I was feeling a little neglected. He said ok but nothing changed.

Today my sister came to my house crying because she had a dream about Jimmy. My husband and I comforted her but I was a little annoyed because the second I let her in my house she ran into my husband's arms. We all went into the living room and sat down. My husband asked her what happened in the dream and she actually asked me to leave the room because she didn't feel comfortable telling me!

I was so upset at this point I immediately left and started tearing up in the other room. I was in the other room for around 10 minutes when I heard a loud sound in the living room so I got up and went there. I could not believe what I saw. I am literally crying my eyes out while typing this up. They were fucking making out. On my couch. In our home. WTF DO I DO? My entire fucking world has just been shattered in front of my very eyes..

I ran out of the room because I was going to vomit right there and locked myself in my room. My husband hasn't even tried to come in. I have been crying nonstop. Please help. The two people I trusted more than anything... What the hell do I do