Is it normal to get intense pain at the injection site after taking Heparin injection?

Hello doctor,

I was in the hospital for 3 days for the flu. A nurse came in and said she was going to give me an injection in my stomach that would help me not to get blood clots. The medication is called Heparin. I told her that I had stomach ulcers before. She said it was fine. I was so sick with the flu that I did not argue. I have never had a shot in my stomach, and when she gave me the shot, it burned and really hurt.

It felt like she hit something. I got one more injection later that day from a different nurse and felt nothing. When I got home, I had extreme pain at the injection site. Then for two weeks, I had pain and severe bruising moving all around, up, and down my right side, only below my waist on the same side of the injection along with the pain. It looked like I had been in a car accident. Now it has been almost a month since the injection. Bruising has stopped, pain is better, but I still have pain inside at the injection site.

I believe that the injection hit something and caused internal bleeding. I am worried that I could start bleeding again. My doctor was not very helpful when I first reported this to her. Kindly advise.