Husband refuses to tell me why he didn’t come home

My husband and I are in our late 20s and we have been married for six years.

We work hard and have a busy social life. I am happy and I always thought that he was too, but recently he went out for drinks after work and didn’t come home until after work the following day. I called his mobile phone, but it was turned off. Nothing like this has happened before and it is driving me crazy.

I refuse to have sex with him because I am convinced he slept with someone else. I feel that I have a right to know what has happened, but he refuses to talk about it. What can I do?