I would say bc of the pregnancy but you said this was going on BEFORE the pregnancy. I tend to go with my gut rather than the "evidence" everyone says to look for. How much do you trust him? Do you honestly think he is cheating or are you feeling that this is what is SUPPOSED to happen given the situation? What else has changed? Has he lost a job/got a new job? Family troubles?

Guys have this feeling that they have to be superman and don't feel okay (most of the time) asking for help. If he consistently holds a role of being the breadwinner or man of the house and something has changed, that can seriously hurt a man's ego. Maybe he thinks you are disappointed in him? Not interested in him?

When was the last time you made special time for each other be it a nice dinner out or even just a movie? Do you guys have things you do together and noone else? Relationships require a lot of work from both sides and "searching" for evidence probably isn't helping the situation. He isn't a mind reader and neither are you. For this to be solved there needs to be straight up honest discussion. His response to a simple talk with you will tell you more than a vanilla smell in his car.