|Question:||I am not sure the meaning of this sentence|
|Term:||up the point I found out|
|Lesson:||EffortLess English Podcast, bad choices|
In this case, the "it" is the fact that her boyfriend was cheating on her. The cheating was referred to in the previous sentence, so she's using "it" in the next sentence to refer back to the cheating. In this case, if you're confused, you can substitute the pronoun for what it refers back to, making the first part of the sentence "The problem is the cheating continued further into our relationship..."
"Up to the point that" in this case means "until the time that."
So the full sentence, with those substitutions, is "The problem is the cheating continued further into our relationship, until the time that I found out I was pregnant."
In other words, her boyfriend continued cheating on her until she found out she was pregnant.