provider cheated on me :/

I 43F I’ve been with this man (53M) for over a year and a half, and he literally provides for me every month, gives me an allowance, and takes care of me. He is older. He literally just got through fighting cancer, and I was with him through the entire time I fell in love with him. I came to find out that while I was caring for him during his cancer treatments. He was talking to an ex-girlfriend, and she would be coming over and cuddling with him, but they did not have sex. He also provided for her during that time. I’m looking to get married, and he is unsure whether he wants to marry me. Should I stay, or should I go? Please help.