Day 1 yesterday of no PMO, but I had sex yesterday with my on and off FWB

Hello everyone, I'm new to FaNop since yesterday, I wrote about myself and my issues on introduced section. Yesterday I was looking forward into my journey. I got off work at 8am then I meet up with my mother at the blink gym we worked out for an hour and half then drop her home. As soon I got home, I did my usual routine shower, eat good meal after workout while catching up new recent episode of the flash. I made sure I pushed myself doing alot of reps (yesterday was chest day) couldn't barely move my arms so I won't have to PMO. It, Happened when my on and off partner text me she wanted to see me. We are not exclusive but have a friend with benefits. I haven't seen her for 3 weeks due our busy schedule. I was hesitant to text her back, but at the same time it just hit me in my mind sexually we have and I see I can release without having to masterbate. she sent me pictures in her underwear of her progress because she trying to gain weight in certain areas and be my workout partner., That right there struck my mind I need some sex. She was already in the area taking her business and said she call me when see at the door. I slept a little until she call then here she is, wearing nice tight sweats top and bottom , her ass showed. We spoke a little catching up then we kiss then so on. We had sex 3 times and she left around 10pm evening. I feel kinda guilty because I wanted to start my journey stop from PMO. I didn't watch any porn or masterbate after she left but did orgasm having sex. I felt like cheated on the challenge especially it supposed to my first day to stop PMO. Its funny because I started this challenge to stop my addiction, It's been 3 weeks since I saw her and she texted me out of the blue in the area wanted to come over. I'm wondering any members here can give me their opinion, advice will help or had similar story to share. Thank you taking the time to read my journal and your comments.