Scared of being a fool?

My fiancee and I have been living together for 1 1/2 years, he's 52 and I'm 40 he's a retired army and has told me history of him cheating on his wife, with his wife and her friend, likes alot of attention and is a big show off. I fell inlove with his comical ways, out spoken personalty, and being a friend. So what to do when you feel like your fiancee is cheating you dont have proof but a gut feeling because of his past, and because in beginning of our relationship he showed he cared, supportive, loving, felt wanted, ask me to marry him, bought me a beautiful ring, car and house. Thats all material and I'm scared because I'm so inlove with him and now I feel like he has me now that he doesnt have to put so much effort. He works more, distance from me, stop wearing his ring, rude, gets frausted easily. I'm confuse?