Omfg I am disgusted !!!

I am fucking fuming right now. I have a 2 month old baby and a 20 month old. I was in the middle of making breakfast for us, I was also preparing some for my daughter. My son was crying (newborn) and my partner was meant to go for a quick cigarette. I had a weird feeling so I went to the toilet and caught him on the floor wanking. I am fucking absolutely disgusted!!!!!

For one he has major back problems yet he can be on the floor like that!!! He denied I saw what I saw yet I saw everything lying fucker. He was saying I saw what I wanted to see omfg red flags!!!! He's still lying because he is embarrassed. I actually don't know what to say. This is vile and makes sense why he goes to the toilet all the time.

EDIT: my daughter could have walked in on him. The fact he did this whilst baby was crying is disgusting. Even the whole street heard him cry. I went to check on him because I wondered what was taking so long. I've dropped this now with him but he knows there's a time and place for this. Not whilst I'm in the kitchen making food and our baby is crying. Makes no sense