She’s given birth she can take your fist. Rather than an oil lube, try a thick lube like like Vaseline. Remove your watch. Try a latex glove to start that helps. Finger her, use as many fingers as possible then start to push in, when you feel the tension from her tightness encourage her to breath, to accept your fist, when she’s moaning like that she’s not concentrating. When you tell her to breath, to focus she will immediately sync with you, she will work with you and then you push past the tightness gently, and once you have the width of your fist accepted into her pussy is when you start to gently fuck her with it. Still encourage her to breath, to be a good girl for you, now she will be moaning again, let her! Pound her pussy with your fist, do it in a slightly in and up motion as most women curve and tilt inside, this will help her to squirt. If you mentally connect her to you during the fisting process, be her master, the wetter and more pleasurable it will be all round. Fisting done correctly is beautiful.