Really not a good idea. Especially if the countertops were plastic laminate, as I suspect they are. Well, the deed is done. You need to find a good clear coat for the top, and I would suggest looking at a water based varathane. The reality is that if you wanted "marbleized" countertops, you should have hired an interior finishes contractor to come out and install a plastic laminate with a pattern you like.
No matter what you put over the latex, it is going to scratch, flake and chip off over the next 12 months. I cringe just thinking about it.
Make sure you use a cutting board, and don't let anything sit on the counter top for an extended period of time. Don't use the toaster up there either.
Good luck, sorry you got this far without asking first!