by me seeing texts on her phone by the second guy, telling her if she was stressed out to "Rub one out".
Wow. Just wow. You have a lot more to worry about than worrying if meds are causing this. I'd be willing to bet that is at an EA, but a PA much more likely.
My ex was on FOUR different meds. It isn't the meds that cause such behavior - they can't create what is already there.
There are moments in this life when you are so confident in the rightness of your actions, that not even for a second do you consider the option that you might be wrong.