How far along?

Bella
I stopped birth control the beginning of October and had a normal period about 5 days long then November I had what I think was my period which was 3 days long and very light. I just found out I'm pregnant and think I'm about 5 weeks. But I'm hearing that maybe my last period wasn't really a period and maybe just implantation bleeding if that's so I'll be way further along then I thought