Should I give recent gifts back to ex-boyfriend?

I broke up with my ex-boyfriend 4 months ago. I have been in a new relationship for around three months. Just after we broke up, my ex sent me really nice gifts for my birthday. Now, four months later, he knows I'm in a new relationship, but still really wants to be friends. I said that that would be ok. I think he still has strong feelings for me. He asked me if he could send me a letter every now and again, just so that I could get something real in the mail other than bills etc. I said okay. Two days later I received a huge parcel in the mail with really thoughtful gifts. When he sent me gifts for my birthday I said I couldn't accept them and he got insulted. I think he gave me these things because he genuinely cares for me. Although he has been manipulative and abusive in the past. If I send the gifts back I know he will get hurt, insulted etc and will damage the friendship. I know that I need to tell my current boyfriend about this even though that will probably make him feel bad as he hasn't given me anything, not even flowers. Do I give the gifts back? and how do I tell my current boyfriend without sounding manipulative?