We need to know much more to come to a single diagnosis about your condition. Exact site and plane of abdomen where you are feeling so need to look and palpate your abdomen. Any how being this vague complaint it might be a lipoma in obese abdomen which sometimes gives you a sensation like that.
Next Steps
please consult a general surgeon.
Health Tips
even mild symptoms which are not neglected and looked into in earlier stages may reveal dangerous pathology earlier and could be treatable.. so never neglect your own health