Sex pill in fiance's car?

My fiance and I traded cars for the day yesterday. In the loose change compartment I found a gold medication capsule inside a clear plastic pill casing. I asked him about it when he went home and he said it's a "do-it" pill, makes you randy. I asked why he'd keep it in his car and he said there was 2 in there but he used one.... with me. He claims he didn't want me to know and that if he were cheating why would he need that pill. ...So he wouldn't need it with someone else only me 😢 Should I be mad?