Hey idk who needs to hear this but your partner demanding a paternity test on your mutual kids is not normal. Like even if they weren't the nominal sperm source's kids, your partner should know you well enough to be aware of that, accept that this is who you are as a person, and be happy to raise your kids regardless. But if you're not rawdogging anyone else and you've told your partner you aren't, and they don't trust you to tell them the truth, get out of there.
You shouldn't date someone who doesn't trust you, or someone you can't trust. But you should absolutely not have kids with someone who doesn't trust you, or someone you can't trust.