Bruising

Hello! I saw some posts about people getting random bruises. But I always get bruising at injection site. One time, on my stomach, I accidentally hit a capillary and the bruise.. Big bruise, stayed for weeks. Now, I switch my area from stomach to legs.. but I did my injection on left leg 2 weeks ago, and on right leg last week. I can see both bruises..

How can I prevent it? I switch from stomach to legs as it's less visible. But I hear people saying that injections in arms work wonders.. but I don't want to have bruises there...