Fiancés often watch black movies during working hours

I feel very uneasy because there is no reason to open that movie in the office hours.

I am 20 years old, studied pedagogy, graduated a year, working as a salesman for a software company. I'm 33 years old, my fiancé, as a manager in a technology company. We love each other for a year, both families know and cultivate for the two of us. Talking about the process of love, we are quite suitable about everything: affection, character, hobbies and sex. Both were open, exchanging frankly with each other so there was no argument. He psychologically, know how to care for me, know how to treat people like that, we plan to marry next year.

Then I found out that I was 4 weeks pregnant, we agreed to get married early this year. Recently, I found out that he watched sex movies during work hours (his brother's web browser history looked at the entire office hours), several episodes each time. I asked him, he said good, see, also said I think a lot. Did you discuss or chat sex with someone to watch movies during that hour? I have previously found him chatting like that with other girls and then addressing him and his wife. During those times, he apologized to me, promising not to do so. I love you so I let it, not think anymore. Now his expression so I feel insecure. Will he betray when I finished giving birth?

The more I thought the more pressure, just worried and crying alone. I want to go away to be a single mom, am I taking this issue seriously?