Super Slow Internet Only NOW!!! Help PLEASE!!! Only After...?

I have a Mac Book Pro that has been very fast for the past year and a few months i've had it. only after this last update (this past week or so) has it gotten extreeeeemely slow! it's stops every two seconds (i kid you not) to "load" or do whatever it's doing! It just freezes and gets that spinny mouse, waits a few seconds, and then goes on... only to do it AGAIN two seconds later! it's driving me nuts!!!! i could take it into the apple bar, but i wondered if anyone could give me a little help. what happened? what do i need to do? i've kept up with all the updates (most... i don't do the bluetooth updates) and it's always run so well and so super fast and i've loved it for that... so what changed? what's different? what happened? i don't get it. has anyone else had this problem? what did you do about it?