Blood is back?

I got my implant (good for 3 years) on December 2018. After 4-5 months of having just spotting and/or little to no blood of menstruation, I don’t bleed anymore. A year after no bleeding and then last week I felt pain on my lower abdomen. I was thinking it might be UTI, but then I thought I don’t even eat or have unhealthy habits that could lead to tract infection. There’s still pain on my lower abdomen but I don’t think it is UTI. There’s blood, it’s a bit dark so I guess it’s “old blood”. I think I’m getting my period again but blood is not coming out that much so that’s probably why it hurts. I stuck up a finger in there to check, and yeah it’s period blood.

Why is it like this? Is it normal that I’m getting my period again after a year of no menstruation due to implant? And what can I do to ease the pain? How can the period blood come out easily like it’s supposed to come out before?