Am I (f23) cheating on my “situationship”(M24)?

Me and my ex are trying to work things out after a few(5) very messy years off and on. Deciding to really work on our trust issues/communication skills together, while living hours away. Things are going decent, my own emotions and unregulated nervous system usually cause issues for us. I can be quick to anger and hes even quicker to shut down. We have established we are exclusive to each other without the pressure of a label (pretty much dating & doing relationship stuff without the extra stress ig). We’ve been in our “situationship” for about 10 months now, seeing each other at least once a month. I know I love him and would love a future together if we can work through the existing issues. Fast forward to this week. A mutual friend expressed a sexual interest in me. Using all my self control to not engage with her throwing herself at me(not complaining at all). I’ve missed sex with a woman so bad and she was an old high school crush/interest so it feels like a dream come true. I’ve been going crazy thinking about her for 2 days i dont know what to do. I dont want to ruin the mostly good thing i have going with someone that is a great person and i can see a future with, especially for JUST sex. But this girl has always intrigued me and although it may not be a once in a lifetime opportunity with her, i know it would be so fun. Also fearful of catching feelings for her as a result of good sex especially if they are one sided. Both decisions leave me feeling kinda shitty & very regretful. I am not a cheater, loyalty and honesty are my biggest values. We aren’t necessarily together, but we have agreed to being exclusive. My brain has been rattled with too many thoughts until i see her again over the weekend. Maybe I should just end things with him to work on myself & give myself a better chance to not be eaten alive with guilt perhaps. ANY advice would be helpful, hatefulness is not appreciated but well understood. Questions can be answered. Thanks.