My girlfriend [F18] is being distant from me [M23]

I’ve been in a relationship with my girlfriend for two years. Since I study in another city, we don’t get to see each other often at best, around 3–4 months a year. She has always been open and honest with me, never hiding anything or giving me reasons to doubt her.

However, in the past six months, our relationship has gotten really rocky. When she found out I watched porn, she saw it as a form of cheating. This summer, we also argued a lot. I have the bad habit of sometimes checking out women when we’re outside it’s not intentional, more like a reflex since I tend to notice everything around me. She also found out I once replied to a message from my ex, but there was no hidden intention on my side it was just a response.

In the early stages of our relationship, my mom made a negative comment about her mom. During that conversation, I told my mom it wasn’t fair to judge people before meeting them, but my girlfriend still brings that up sometimes. She says she doesn’t fully trust me, and recently told me she needs space to “find herself.” She has become distant, and since this is my longest relationship so far, I really don’t want to lose her. Any advice on how to (or not) act in this specific scenario?