Fucking my Girlfriend's Mother

I'm David 22 and early last month my girlfriend Beth had to go away for 2 weeks. I would be awaiting her return as we and a regular sex life and would miss her a great deal. The next day after Beth had left, I got a call from Pauline 46 Beth's mother. Pauline wanted my help moving some large rocks in a rockery she was redoing. Pauline divorced and only had one child Beth and with no other people around to help her she called. So I went over and helped her with the rocks. While moving the last big rock I split my pants and Pauline said she would repair them for me. So I removed my pants a waited in my shorts for their repair. Pauline repair them and just as I was putting them back on, she asked me to fuck her. I was a little shocked at first, but also horny and agreed and so we fucked twice that day and have been fucking regularly since then. I've moved in with Beth and Pauline and as Beth works shifts, I fucked Pauline and it's just sex as Pauline said just for mutual enjoyment.