SO is getting upset with me so torn up about our miscarriages and is talking vasectomy

We just had our third miscarriage.  I have one five year old.  I am now seeing a rheumatologist and am a high risk pregnancy.  My SO keeps talking about getting a  vasectomy for a number of reasons.  He knows that we would be higher risk for premature labor, stillbirth, or more miscarriages. He thinks I should just stop trying.  I'm getting so upset every time he mentions it.  At this point I feel like I need to not tell him news when it comes to my health and body.  I want a baby so badly, but if I have another miscarriage I'm afraid he will secretly get a vasectomy.  I don't know if I could stay with him after.  It would kill me. How do I convince him that a vasectomy is not the answer?  I'm so scared that he will get one without my knowledge.