Ok, the person above was super condescending, so I'm going to answer. No, there's a. literally no way she could have become pregnant, and I'm sure you know that too. b. your brain knows that, and it's a struggle to trust the rational parts of your brain, but you have to let it speak louder and louder, you have to trust it more and more, in order to move away from anxiety. Think of the brain like a muscle, rather than an organ, one that has to be trained in a certain way in order to become more rational. Often I have extremely hypochrondriacal fears, which my irrational side tells me are real, and it is incredibly difficult not to trust this frantic, extreme side of my brain, but I know that it's not correct.
On another note, you were likely aiding the sex-sale industry which is troubling! Sex is safer when you do it with someone you trust, who you can ask about their contraception choices. But, sex itself is an anxiety-inducing act for a lot of people for a lot of reasons, which is even more reason to do it with someone you trust.
Well, you didn't "have" to go on Lexapro, you chose to. You could have chosen to see a psychologist who specializes in anxiety treatment or done other things. So you don't "have" to be on Lexapro. Now, the difference between anxiety and fear is important -- fear is rational if there's something rational to fear, and obviously, if you know anything about biology, this fear isn't rational. If you don't know anything about biology you're not ready to be having any kind of sex yet and need to learn how it actually works, but I suspect from your post you do know it's impossible to get someone pregnant this way. Frankly, it's amazing anyone ever gets pregnant -- it's a pretty difficult process with a lot more failures than successes, but you get lucky -- or unlucky -- sometimes so you have to take precautions. But you obviously have to get the sperm to the egg and you didn't go there and I think you know that. Anxiety, as opposed to fear, is irrational and useless -- it's creating discomfort in addition to that which life throws at us anyway. When you fear something, you either face it or avoid it and the situation ends. When you're anxious, you create a situation that doesn't end. Focus on your anxiety problem -- real fear you can deal with.