YOU ARE NOT STUPID!!
Just a loving wife who just got blindsided! I am so sorry you find yourself in this situation. You do not have to make ANY decisions right now. You have been dealt a heavy blow and are in shock.You have a lot to think about and he has a lot to PROVE.
Fair warning, you are probably right that there is more to the story. WS lie and try to diminish what happened. The truth usually comes out slowly (called TT-trickle truth) And it sucks!
There is a lot of information here in the healing library and on the forums. Read, read, read. You will see that there is a "road map" of sorts, things that must happen in order to put the pieces back together. Everyone's story is different but there are some basic things that need to be addressed for everyone. Getting the truth, NC, transparancy, rebuilding trust etc.
Right now, take care of yourself. Don't worry about making any decisions. Try to eat, get some sleep and give yourself time to get used to the fact that things are different now. You will get through this. You have strength in yourself that you don't even know exists. *hugs*