Embarring question about my boyfriend's uality...?

I hate to have to do this, but I have no one else to talk to. When I first met Sam we were both going through an experimental stage, he was seeing multiple men and I'd had one encounter with another girl. We started out as friends, became best friends and then lovers / partners. Of course this meant we were monogamous with eachother so the issue of sleeping with other people, men or women wasnt something we spoke about. It started to bother me when everyone I knew including my parents commented how they thought Sam way gay. Admittedly he does have a lot of gay qualities but we were so in love and were so dedicated to eachother everyone accepted us as a couple. We have no been together for 9 years, we live together and he has recetly proposed. My only worry now (apart from his sometimes feminine qualities) is that I have caught him searching the internet for gay and phone dating sites. I found messages on his mobile from gay websites offering him previews etc.