Do you really need for us to point out the obvious to you?
Did those condoms just leap into his truck? Perhaps the Condom Fairy deposited them there.
Sorry to be flip but, really, this stuff is relatively obvious.
I suspect that the communications with his cousin may very well be fine. The rest of it, not so much.
But it's also troubling re the texts - if he's keeping them from you, how are you seeing them? I take it that you're snooping. Not right, etc. but of course this is how you know (but, really, you've got rather good proof without the snooping. Condoms in two places would have done it for me - I could almost
see the motel excuse but the truck? Nope. Those did not just magically appear in there. Even if he left his truck unlocked, even if he let some pal of his borrow it, the chances are microscopically small that the condoms got there in any manner other than him putting them there. As to whether he used them -- and you're only finding the remaining ones -- is not something that can be proven. But he's got the means, yes?).
In any event, you already don't trust him. And you don't seem to have a good reason to, either.
Consider this -- as they often say in old movies about murder cases (and, BTW, these statements are not of a legal nature or for legal advice. I'm just trying to make a point and I keep thinking of old detective stories), did he have --
- that seems rather possible, seeing as he's complimenting other gals in text and then lying to you about it
- condoms in the truck, condoms in the motel; here a condom, there a condom, everywhere a condom, condom!
- if he's off to motels, I am assuming it's for business travel. I used to be a business traveler. Not everyone who goes on the road is having an affair or contemplating same, but the fact that he is outta town certainly gives him chances that just hanging around at home would not make possible.
So -- why are you sticking around?