Parenting Through the Period

Sometimes, I think back on my C-section 18 mos. ago and regret not telling the doctor to just take my uterus out with the baby! I don't need it anymore--I've had my tubes tied, I'm done having kids. So, why on why do I have to go through the pain and agony of periods every month?! Let me tell you, my husband and my kids would probably be much happier not to have to tiptoe around me for a few days every month! Parenting is hard every day, but crampy, bloated, headachey days--it is really hard! How can I explain to my 18 month old son that I don't want him to sit on my lap because I'm cramping and his sitting on my lap is excruciating? I can't! So, like a lot of things in motherhood, I just grin and bear it. How do I tell my four year old that I'm too tired to push her on the tire swing or take her to the park? I can't; I'll just pray for rain and blame lounging around the house on the weather...