How do u know if your with a cheat?

i have been with a man for 3 years and for the first time after a night out with his friends he didnt come home, not even a phone call i rang him at 9.30 in the morning and he told me he had fallen asleep on a train and he was on his way back. we had got engaged weeks before this but am i being paronid. i also have a 1 yr old with him wot do you think. please help x