What to do regarding relationship

For context, I have been in a relationship for the past 4 years. This year, we bought a house together and have been happy. However, I go through periods where I am just not happy, and or get uncomfortable about being in the relationship as I don’t trust what I want (typical anxious attachment style). When I feel this, I often will look for advice, space and sometimes pleasure outside the relationship (porn for eg). Recently, a friend of mine has been telling me about struggles in her relationship. I know I find her romantically attractive and she has told me she likes me too. Although I could see us as an item, we are both tied up in our own relationships and have both bought houses.

When finding out this information, the guilt from this basically emotional cheating made my mental health take a turn for the worst. I still haven’t told my girlfriend, but I have stopped messaging the other girl. The other girl is upset by this, but I don’t want to mess her around, nor my girlfriend currently. It’s just my current relationship feels a bit dry and needs spicing up, which is difficult to communicate to my girlfriend without her getting upset.

The advice I am looking for is really what to do. I know if I left my girflfriend for this girl, it would be messy and no guarantee it would work. On the other hand, I don’t want to waste my girlfriends time, nor do I want her to experience me feeling unstable in the relationship. I know I am a massive A-hole for my actions, I just don’t know how to navigate this.

I’ll happily answer questions