Implantation bleeding advice

[Sammyclaire22]

I'm about 4dpo and just had a trace of fresh blood- I only noticed as it marked the sheet! I'm out of practice with the details of ttc as this is month 1 for baby 2. Isnt this too early for implantation bleeding?
My cycles are super regular so very unlikely to be af (not due until the 22nd +/- a day)

Freaking out a little bit now as my first pregnancy was ectopic and now I'm worrying that it's implanted in my other tube as surely it's too early to have reached the uterus?