Before marrying my husband our relationship was OK pretty good but as soon as and I mean immediately after we were married it all went South. My SS live with his BM until the last CS check cleared (if you know what I mean). He graduated HS and moved in with us. I try  to treat him as my own son he refuses to be respectful walks through my home not speaking to me and we communicate through text messages he only responds to anything having to do with food. Fast forward...my daughter was here she saw him looking through the trashcan with his phone as a flashlight for something I paid it no mind. A day or two later I saw him in the trashcan with his phone for a flashlight and thought I saw him lick his fingers. I thought surely I must be mistaken he cannot be licking his fingers after having his hands in the trash. Day or two later I saw him reach in the trash and come out chewing on something and I said to myself no can't be. Then I began to watch because I was really suspicious and curious to know what was really going on so I would watch while he was in the kitchen through the cameras and he would go to the trashcan first as though he were looking in the refrigerator. One day we have pizza left over so I threw it out and I noticed he went to the trash with his flashlight on his phone took something out and put it in his pocket I confronted him and of course he lied and said he would never do that.Long story short I told him I knew he was lying I told him I loved him we love him we live in almost 4000 square-foot home not hurting anything fully stocked fridge. Pantry is full no need for him to go to the trash like he's homeless and just when I thought I'd gotten through to him I saw him today July 31, 2021 with his new way of eating out the trash.Now he took a paper towel after seeing some thing they want it in the trash took the trash bag that was not even close to being full out the house to the big trashcan outside and I took them a long time to come back inside. Looking through cameras I saw him put some thing in his pocket while he was coming back inside and when he got inside either he had something big in his pocket or he was super happy to be back inside if you get my drift.I'm really not sure what's going on with him super concerned and I don't know how to handle this. My BioS has mental delays and challenges and he has never done anything like this so I really don't understand why this 20 year old who has never been diagnosed with having any type of neurological issues would be doing this. He hates me so much because I'm not his BM? He'd rather eat out the trash than ask for or just get it out the fridge? He waits for me to throw food out. I have not done anything to him but try to love him in the absence of his BM. Any suggestions on what to do or how to handle the situation and also uniqueness.