How Early Can I Test?

Fairleigh
Hi ladies! Just wondering how early I can test? Last period started Dec 1 so period is due the 28th... but getting lots of symptoms: bloated, nausea, sore boobs, dizzy, headaches, spotting for 2 days around day 16 of cycle (implantation spotting?) My cycle isn't exactly regular so I'm unsure if this is anything? Thanks so much for your help! Merry Christmas & baby dust xx