When should I test?

I think I'm roughly between 3&5 weeks pregnant but I'm unsure when to test, my last expected period came very usuaual, mine usually last the full 7 days and are and heavy as hell, and my last expected one came for 4 days and was super light! On the 9th I also started spotting, it's stopping though it'd now be the 2nd day of spotting, is it too early to test? My next expected period isn't until the 25th of this month! I have 3 first response pregnancy test waiting to be taken, any advice would be great :)))