is he lying or telling the truth

Df is a Leo, who works 18 hours a day and I haven't seen him since he was at work and I was in the process of getting us to move to our new home. He's cheated on me before years ago and I've stayed. He came home from work with a mark on his face and I cried my eyes out as soon as I seen it since it looks like a tiny hickie it's located by his jaw bone towards his ear. He says it's a ring worm from standing in the hot heat and "if it was a hickie why would it be by my ear". Now I told him that, he has to be around someone with a ring worm in order to get one. I never came up close to it, the "mark" its dark like a hickie but not bruised looking like and DF is really tan! What do you think? Stay? Go? I'm stupid? He's lying?