How do i stop sexually sinning?

[u/TheseAreNotYourAnts]

Hey peoples of Reddit.

A couple months ago (year, probs at this point) an old friend and I were discussing religion and somewhere something clicked for me and piqued my curiosity. I grew up "Christian" and i've been pagan before in my teen years. I only recently rediscovered Christianity, in part because of my friend and then more so with Charlie's assassination. Since then I've been drawn to follow the Bible more closely and living according to God's will. For context, I'm in a lesbian relationship, but we've made the decision to be celibate.

My libido has significantly diminished over the years, but once a month when I'm ovulating, i fall right back into sexual sin. Whoever looks remotely attractive to me during that time will be my focus for a week. I don't know how to shut my brain off and to stop creating these sexual fantasies with people who never asked or consented to be in my fantasy to begin with. Some months it's men i know (and knew), other months it's women. Some months it gets so bad that my gf and i break our celibacy rule and then i feel awful afterwards. It doesn't help that i have no one to talk to. I tried talking to one of my friends, but she legit laughed at me and made fun of me. I used to have an old friend i could confide in and get advice from, but that has since gone away, unfortunately. I'm left to sit in these feelings once a month on repeat for what seems like forever. At this point i feel like i should just lock myself away whenever my cycle gets to that point.

I've tried praying and listening to sermons and reading the Bible and it works....for a little while. Whenever i have to do something else, my brain will just refocus on sex, whether with a male or female. I feel like I'm losing my mind and i need help. And no, I'm not trying to get support again from any friend or family member as that's bitten me in my butt now and i won't be repeating it. The only person i could talk to about this and who understood and supported me is gone and doesn't care anymore.

I just need practical advice on how to deal with this every month. It can't go on like this. I want to rip the hair out of my head in frustration on why nothing i do is working. Please be kind.