Did my boyfriend cheat while he was away?

Would you be concerned your boyfriend cheated on you when he came back from a trip without you and had a deep scratch above his ankle? The scratch cut his skin and it bled. He also had a bruise on his bicep. A small scratch on his shoulder blade. A round circle below his knee (looked like tape worm but probably isn't) and a scratch above his knee cap as well as a scratch on his rear end.

Also, just after he got back, he tried bondage and rough sex with me when he always preferred slow and gentle sex. He seemed more aggressive than usual. He seemed to have more vigour and a renewed sex drive as well. In the past, I am the one who was the aggressor. He almost always followed me lead. Why this sudden change while he was away and why the marks on his body?

When I talked to him, he said it is all in my imagination. That I am being paranoid. That he has always been true to me and that I can trust him.