I am dating a guy. We recently went out of the country together. When we were away, he let one of his guy friends (whom I have never met) drive my car, and he lied to me about it. I found out because I found a receipt in the car, and when I asked him about it, he lied initially. I asked him again, and he came clean. I was annoyed, but tried not to get too upset about it. I have a tendency to overreact. He didn’t understand my being upset. Was I wrong for being annoyed by this?
LemonVibe 
OK this guy is gaslight ing you because that’s illegal. It’s your car and he let a total stranger to you use YOUR car. This isn’t even the beginning of your issues. He lies to you. He makes you feel like you are going over board (gaslighting). He effectively had your car stolen. It’s not his car. You pay for it. Imagine if the guy had used it as the get away car in a burglary or hit a pedestrian, etc.
Get rid of this boyfriend and change your locks and passwords as fast as you can. Worse is coming from this man.