My husband cheated on me with a sperm donor

I (f26) live in the UK. I met my husband (now 33) when I was 17. He looked younger than me when we met. He is not conventionally handsome, but he has always looked young for his age. He is still very childlike and looks like he could pass for 21. He is autistic and not the most clever person, but he is a hard worker and has always been dedicated and loyal. I know a lot of you are going to hate this post, I'm sorry. I have an extreme medical condition which affects my fertility. When we were first trying for a baby, we went through five rounds of ICSI with our own eggs and sperm. The first round we made a baby, she miscarried at 14 weeks. The second round we made another baby, she is now six years old and extremely bright and intelligent. Because we were unsuccessful with our own eggs and sperm, we decided to use donor sperm. I became pregnant with a baby boy. I received his donor information, and the baby was born extremely bright and intelligent. My husband knew that I was using donor sperm, but he didn't ask questions. The baby that was born with donor sperm was a result of IUI (sperm inserted into the womb), we asked for the same batch of sperm to be used and we did multiple rounds of IUI. For each round of IUI, a new batch of sperm was used. In total, we did five rounds of IUI, and we had three babies. We received the same batch of sperm each time because we asked for it, and we were told it was the same donor. I have always known that genetically, my children are not related to my husband. However, when I was pregnant with my third baby, I began to wonder how my children looked so alike, despite using donor sperm. When my third baby was born, I looked at the babies side by side, and I couldn't work out which one was the 'real' one. My husband and I both look very different, so the fact that our children all had the same facial features and hair colour was unusual and confusing. I asked my husband if he wanted me to do a DNA test, and he said it was unnecessary. I asked again, and he said it was not a good idea. I asked a third time, and he finally said yes. The DNA test results said that my youngest child had 0% DNA similarity with my husband. I asked him if he knew what the results would say, and he said yes. I asked him why he lied to me, and he said he didn't lie. I asked him what he meant, and he said he didn't want to hurt my feelings. I asked him if he cheated on me, and he said he didn't cheat. I asked him what he meant, and he said he didn't have sex with anybody. I have confronted him four times, and he has said he didn't cheat on me. Although he cheated, I know he didn't have sex with anybody. He used a sperm donor but he doesn't want to admit it, or he doesn't know what he did. I have spoken to a lawyer, and the sperm donor will be contacted. Pity incel, sperm donor cel, whatever you call it. When I find out who the donor is, I am going to cause a shitstorm. I will make sure the world knows what happened. I lied to my children and told them he was their father when he wasn't. I was brainwashed by him and I didn't see what he did. I did, however, ask if he cheated on me, and he said he didn't. I will make sure he regrets doing what he did.