"Mommada" is an Internet slang, usually used to express affection, liking, happiness or friendliness. If a married man sends you "mommy" pictures, it may be because he feels that you are closer to each other or he has a crush on you, but it does not mean that he has any unfaithful behavior or intention.
However, if you feel that this man's behavior makes you uncomfortable or offensive, you can tell him directly how you feel and ask him to stop. In any situation, it is very important to respect other people's feelings and boundaries.