What Causes Abdominal Tightness Post Abortion?

Hi, I had an abortion about 2-3 months ago and at that time I was 7 weeks pregnant. I noticed that after a month or so I would have this tight feeling in my abdomen that would come and go and now recently the feeling randomly occurs in my stomach. I have been going on my menstrual cycle as per usual and my belly is still its normal size although it becomes bloated every now and then. I m rather concerned with what the problem may be and your response would be greatly appreciated.