There may be trust issues but there is also a major lack of communication. You are attempting to communicate with your fiancé but it seems that he is either unable or unwilling to reciprocate. You’re focused on the possibility that he may be cheating. It is an understandable concern because of what had happened in your previous marriage but it may not be a problem in the current relationship. His moodiness and inability to communicate could be a sign of his unhappiness or a number of other unidentified problems. The trouble is that you don’t know because he won’t communicate.
Before you get married, it is important to explore these issues in greater detail. You need to feel secure in your relationship. You should not get married until all of these problems are resolved. They will not go away once you are married. In addition, a lack of communication is a serious (though solvable) problem that should not be minimized. It has led to the breakup of many relationships.
Couples counseling is highly recommended. If your fiancé is unwilling to attend therapy, then you should go alone. It will allow you the opportunity to receive an objective opinion about the relationship by a trained professional. In addition, you can also freely examine your feelings about the relationship and address your unresolved trust issues (and receive an opinion as to whether trust is the issue). The therapist can provide necessary guidance for these problems. I wish you the best of luck. Please take care.