Wife got pregnant 2 months after my vasectomy how do I confront her?

My wife (mother of our two young kids) recently told me she's pregnant and seems really happy about it.

The problem is,I had a vasectomy exactly two months before she conceived.I haven't had my post-vasectomy semen analysis yet,but the timing makes it impossible for this to be mine.I strongly suspect she got pregnant by someone else.I'm devastated and angry.How do I break this news to her and confront her about the pregnancy? Should I wait until I get my semen test results first? Any advice on how to handle this conversation,especially with two kids involved?Looking for practical steps from people who’ve been through something similar.