Husband assumes the baby isn't his?

So I, F/21 ,just found out I was 4 weeks pregnant. I told my husband, M/22 expecting he'd be understanding since it wasn't planned but he always talked about how impatient he is to have kids with me. We've been married for 2 years now. I feel like i'm being gaslit into not being hurt by his first response, which is "if it's mine / dna test". We've been arguing about it and it just makes me dread the fact that i'm going to have this man's baby. He says i'm "overreacting and to prove that it's his and it's a normal thing to ask"which I understand his right to want a dna test and i'm 100% down for it but I just didn't expect that to be his first response. I'm fully aware of the consequences of my actions from raw dogging, I just expected to have him be like "we'll figure it out together"or ANYTHING else. I just don't want to be an annoyance if I genuinely am just overreacting. I've never cheated on him. I fear that i'll have a miserable motherhood and have resentment from my husband and child. I just want someone to elaborate why i'm overreacting so I can understand. I do hold onto things strongly and for a long time. It's like I genuinely don't get over anything. Something is either all the way bad or all the way good with me and never in between and the constant assumption that i've cheated already gets to me but this just got to me the most. I've never cheated or done anything wrong by him. He has cheated on me in the past so I do believe there is some projection there but I genuinely have not done wrong to him.