Paternity test - sorry long post

Hey all.. so i'm just looking for advice here. I've been with my boyfriend for a little over a year now, we barely ever argue or fight and get along great. After telling him i was pregnant, he kind of went into shock and brought up a paternity test to make sure it's his. Ive never cheated or given him a reason to not trust me, but he has been cheated on in past relationships and stuff. We dropped the subject, now just today he brought it up again. And honestly it hurts, i would rather not do it because it would be out of pocket that we don't have right now, and i told him there's no reason to doubt. He said it wouldnt be done. We were also just talking about what who we think the baby would look like, which then turned into if the baby doesnt show resemblance to him at all he wants the test done. I tried explaining to him with genetics you never know, i have a friend whose son looks exactly like her and barely the father at all. I'm just upset that he would even bring any of this up and he should be able to trust me, regardless if this child favors me or not this is still his baby. Any thoughts?