I was wandering if anyone knew how or had any ideas on how to record cell phone conversations from a long dist

My husband works on the pipeline and has recently left home to stay in a motel room with his friend.His whole attitude towards me has changed since.I can't even call him and have a normal conversation with him.He jumps to his defense if I just ask what are doing tonight or he'll let me go because he is always busy.We were just fine before he left.My gut instinct tells me something is up.He also seems like he starts an arguement and says the most hurtful things he can think of to deter me from calling him.He has his personal cell phone and a work cell.Any Ideas on how I can find something out without him being aware?