Was it stupid to get upset about this?

So my boyfriend and i have been together for almost two years and we've never had sex in a vehicle (this is important to the question, hahah). Well the other night we were hanging out with a few people and him and another guy were talking and they somehow got on the subject of having sex in trucks and my boyfriend told him about his first truck and how "the seats went all the way back and it was perfect every time" and for some reason this really upset me because he absolutely refuses to have sex with me in any vehicle ever even tho I've told him I want to several times. He always says it doesn't sound appealing to him.  Around the time he got that truck he was with his ex that he dated for three years that he still sometimes creeps on Facebook. So then j thought of him doing her in the truck and THAT got me. I was visibly upset. Was it stupid of me to get upset? I'm really insecure and it sucks