Hey, you're not alone...there's so many people I've been trouble shooting with for this exact issue for WEEKS. None of us are super techy but one thing that has helped at least get you to the main menu is to move all the files in "saves" to a different file temporarily ( I just made a new folder on my desktop and moved them there), then relaunch your sims app. It should take you to menu, start a "new game", make a random sim and save it. Then move all your saves back into the savers folder and relaunch the sims. This has allowed most of us to load into all previous saves, except the most recent save from before the update....Which still sucks because for most of us, that is our main save file. Feel free to give it a go but it seems the update corrupted the most recent save file. Some people found that when selecting your saves from the menu, there was a repair save option and that has solved this issue completely for some...but others not.
It doesn't help that EA hasn't put out anything to acknowledge this error with their update. But this is as best as we have figured out at this point :(