Hi,
Constipation shouldn't be considered 'normal' (it's not healthy), but it's a common problem and can happen for many different reasons. In your case, you might have extremely tight pelvic floor muscles that take longer to relax after sex ~ if you want to research this, the term is 'pelvic floor dysfunction', to see if it matches your symptoms. Other reasons can be due to certain medications/pain relievers, poor diet, digestive disorders, stress, dehydration, pelvic floor issues, and so on. To take the guess work out of this, consult your gynecologist... Meanwhile, you might want to try taking preventive measures before sex. For example, you can increase light exercise (walking/ cycling), make sure you eat light meals, drink a tall glass of water every hour throughout the day, use a natural stool softener or herbal colon cleanser capsule, and add more veggies/fruit to your diet. Stay away from heavy, carb laden foods and stimulant laxatives. If none of these suggestions seem to help, speak with your doctor for further advice. Take Care :)