Found condom wrapper in my car

today I was out running errands with my sister when I went to the back seat to put my stuff away I noticed a condom wrapper laying on the seat. Not hidden... Just out in the open. My car has 3 row seating. The wrapper was not in the 3rd row my guess is maybe they were and he threw it over the seat? I’ve only had this car for a little over a month. I didn’t clean it thoroughly but I cleaned enough to notice something. My bf is it blaming it on the person that had the car before me which I think is ridiculous. He has used my car so many times that there’s no way for me to even backtrack. I do not have the strength to even piece 2 and 2 together. I have 2 kids I am in the back seat very often ! Am I being naive to really think it wasn’t him... the whole time I questioned him he smirked and smiled and said he could not answer without smiling because of “my seriousness”

***Update*****

Thank you ladies for you kind words!!! After giving this some thought...I would have notice the condom when I put my kids in the car before picking my sister up. But it wasn’t until after my sister was alone in my car and I was putting stuff away until I noticed the condom. I know it sounds seems crazy but I have every reason to believe my sister planted the condom there. I didn’t ask her and I don’t plan on asking her because I know 100% it was not there prior...Sucks my blood sister would want to cause me this kind of stress and break up a home. My boyfriend has never cheated and because I found a wrapper it’s easy to point and blame him. When I found the wrapper she kind of acted as if nothing happened. And then that was the end of that she really didn’t say anything else. Which is suspicious because I would want details if it was the other way around? We spent the rest of the day together and she could clearly could see I was pissed and she knew Why! And still acted as if nothing was going on. Sorry for my rant thank you guys for listening ❣️❣️❣️