I see communication and trust issues here.

As Euryleia said, if you don't want bruises, then you should make that clear as a limit and he should respect that.

Now, if you do bruise more easily than most people, then it may take some adjustment on his part to find the level of intensity that won't leave bruises -- bruises may occur accidentally as he adjusts to that, but you should have a comfortable sense that he is trying to adjust.

If you've been clear that you don't want bruises and the response is simply "you bruise easily" with no attempt to adjust to accommodate that limit, then I would think that's a significant problem that you should carefully consider. The key here being "clear" -- clear communication is sometimes difficult. When I want to be sure something's clear, I use the "tell me like I'm five"-approach: brief, concise, no metaphors or innuendo, nothing that could be misunderstood.

"I do not want bruises; bruises are a hard limit for me" might be a good start.

If it's a sometimes thing, be clear about that: "Bruises are okay most of the time, but I'm going to the beach next weekend, so none until after that date." (Or "I have a doctor appointment and don't want to have to explain: 'Hey, doc, they're consensual'" -- always a fun conversation, I hear.)

If you find yourself feeling that you've been clear about it, but he's not making a good faith effort to adjust, then you have a problem.

The trust issue I see is that you're sure he's intentionally causing bruising, but it sounds like he's saying it wasn't intentional (that you bruise easily). If you truly don't trust he's stating his intent, do you really want to trust him to keep putting you in a vulnerable position?