@TXC_Rafael USE REAL BULLETS, not those watergun pellets (does such a thing actually exist? if not, trademarked as of right now :P). Just kidding, but yea multiple people have experienced the same things you have, as you can see in this thread alone. I've had it happening since the day before the actual new season went live.
It was weird cause in the previous 4 seasons I've never had that issue this prevalent. Once in a while it might happen and I'm talking days or weeks apart in a couple of games, but not to this extent. It was minor, like you shooting someone who went around the corner, you know you hit 'em but saw no damage indicator, afterwards it was fine again. That I could chalk up to the servers not keeping pace with client. But now it seems like it's almost in every game.
I still think it's the game not updating fast enough so stuff happens that the game hasn't processed, cause for me it only happens with fast weapons like the havoc or the R99. This is likely due to some new code or by servers being flooded with new info... hope to see a fix shortly.