I don’t think this is about “quantity” of loving. It’s more about difference. You are coming to this relationship with a first time love. He’s bringing a history of loving (and losing) other people. That difference will show itself in many, many ways as you develop this relationship.
Neither of you can erase his history. You shouldn’t. It’s part of what makes him who he is. If he separated amicably but finally from prior loves, it is unreasonable to demand that he cut off all contact.
Of more concern to me than the difference in history is that he continues to show you pictures and talk about his past even though you have told him that it troubles you. It may be that he thinks this will help you get over your jealousy. If that’s his motivation, it is obviously not working. But if he gets something out of making you jealous, it’s a big red flag.
Rather than complain about his behavior, see if you can find out why he persists in doing it. Is this behavior perhaps why other relationships didn’t work out? If so, it’s his issue, not yours. Is he really trying to be helpful? Then he needs to find another way to reassure you.
It’s also true that you may be over-reacting. Without more information, I’m not in a position to say.
What I do know is that it takes two to create this kind of impasse. For that reason, I think a few sessions with a couples counselor is a good idea. A counselor can observe how the two of you interact and can make suggestions for getting past this problem.
I wish you well,