I'm worried because I seem to bruise easily. Why is that?

I think my skin type tends to bruise easily. I’ve heard there are different types of bruises, and I’m worried that there might be some health issues. Even a slight bump can cause a large bruise right away. Sometimes, I get bruises without even remembering hitting anything...

Someone once said that it could happen even in sleep, but still, I wonder if there's any reason to get hurt enough to bruise on an empty bed.

I always get a bruise after getting an injection, even if I don't feel any pain. My companions who received the same injection don't have any issues.

Is it just because my skin is sensitive, or could it be related to a blood issue, or perhaps some other health problem? I'm curious about it in many ways.