Baby sweating or peeing or???

Ok so last night and today I began to notice that when I get baby out of bassinet his back is completely wet through his clothes, I assumed his pee was leaking out of his diapers so I’m waiting for my mom to pick up a different brand / sizes in an hour but just now it happened again but his diaper was completely dry and I smelled his sleeper and it didn’t have a smell but his skin feels cool to the touch so I don’t think he is too hot I do not know what is going on or if this is normal help lol