3 weeks after should be pretty safe if you tested negative at that point. Especially since chances you were ovulating that soon after are pretty low (but not impossible). Just make sure you use a real birth control method next time.
I’m in the same boat gotta retest in a week even tho I missed my period but if you breastfeed it won’t be regular for a while. But 3 weeks after you should be in the clear!
Never trust the pull out method.. I’m now 24 weeks pregnant because of this 😂
Unfortunately you can get pregnant on pre-cum. However I’d just take a test in a week or so, or if you miss your period. That way it’s more certain.