Ughh I need help

 I need advice ! Me and my bf have been strong for 8 months I recently found out I am 10 weeks ! And we are beyond excited !! But the other day he was acting distance come to find out he's talking to some girl at work . He told me it was about work but today I was playing on his phone and she txt him with a picture so I went to it and I saw that he asked for a picture ..... Wtf .... I need advice asap . What should I do ? Have you even delt with this ? I'm lost. Sad . And really disappointed