AIO to an Earring being in my Husband’s work truck?

My husband and I have been together for 25yrs. During those years we have had some rough times and I've thought he was cheating. I was even planning on leaving him up till about 6 months ago. That is when he seemed to do a 180 and started doing and saying all the things I needed him to for me to stay. So of course I've relaxed and gotten comfortable. Like many couples in long term relationships, we don't have as much sex as we did in the beginning. Yet I've noticed and said something about how he doesn't seem to want it at all. He doesn't make me feel sexy or wanted, just comfortable, like a best friend almost. Anyway, two weeks ago he started driving a work truck from his company. I've road in that truck several times and I know for sure I've checked my makeup in his visor mirror in that time frame. Well yesterday I went to check my makeup and saw a red stud earring shoved into the material on the outside of the visor. He said its been there and it must have been from the guy who had the truck before. He even said the guy he carpools with pointed it out a couple of days ago, so there is no way it wasn't there before, I just didn't see it. I'm sorry any woman would notice an earring in the first 20 minutes of being in any vehicle much less her husband's work vehicle. The way it was stuck in the fabric of the visor seems like a side chick thing to do too. Like it was meant to be found. Of course he goes off about me not trusting him and how he doesn't have time to cheat and how we have been getting along and I'm going to ruin that… well I can't shake the fact I know I would have noticed a red stud earring the first time I was in his truck. So am I overreacting, or is my husband cheating?