It depends on what the intention of the card drawing was. If your boyfriend just told you to draw a card with a question in mind, then you need to ascertain by other means (like asking him) whether he's cheating or not. Don't rely on the turn of a card to determine your most important decisions. If there was another question involved, there are other meanings for the Jack of Club, such as entrepreneurship, an impulsive person, or someone with an open mind and outlook. It's equivalent to the Knight of Wands.