It has got something to do with your digestive system. Just make sure you eat healthy, have lots of water, and have an early dinner. Hormonal issues can be thought of later.
Next Steps
Follow a healthy lifestyle for a few weeks. if your problem persists then we have to take some medications that help digestion fall back into place.
Health Tips
These will help:
1.have 30 ml x your body weight in kgs( ex: say you are 50 kgs, have 1500ml of water)
2. have dinner before 8pm.
3. reduce refined
sugar and salt
4. take your veggies regularly
5.reduce oil I food
6. never avoid breakfast
7. stay happy, keep yourself involved.