My boyfriend doesn't believe me

So we all know that precum can have sperm in it (I hope we all know) but anyways I'm not on birth control for the moment. I'm going to get an IUD soon but for now we are using condoms. Last month we had a condom break on us for whatever reason, in pretty sure because it was too old. But it broke, he didn't cum but I'm tracking my cycle and it was my fertile week so the next day I went and got myself the plan B. I just finished my period and I told him we were in the clear and he was like "I still don't understand why you had to do that, it's not like I came at all and I don't understand why we have to use condoms because I know when I'm cumming" and I said "it doesn't matter, precum can have sperm in it" 
He said "no it doesn't, I don't believe that at all" I was like 🙄🙄🙄 of course you don't. 
Then I googled it and showed him, he still just blows it off. He said "I don't think you would have gotten pregnant if you hadn't taken plan B anyways I think you wasted 60$ for nothing" 
I told him "I really don't care, I'm just glad I am not pregnant, I'm getting on birth control within the next month so we don't have to worry about it, but we are NOT having sex without a condom and I'm buying new condoms because if you haven't noticed yours are crappy because they're old" 
He rolled his eyes like come on you butthole. 
Atleast I'm being safe about it, this is why I haven't gotten pregnant in the past 2 years we've been together because I do everything I can to be safe. He thinks he knows everything about his stuff and obviously he does not. The next time I see a doctor for my birth control I'm going to ask him to write a note to my know it all boyfriend telling him about precum just so that he's heard it from a professional. It's just super annoying that he thinks we are like invincible from getting pregnant.  
I am stoked to get an IUD, it will make me feel more in control of these things. 
And the plan b didn't affect my cycle at all. I had side affects like acne and breast pain but my period came perfectly on time.