Implantation bleeding?

I think I might be pregnant and I really cannot afford to be right now and it's stressing me out so I need we other people's opinions to maybe help me feel better. I had sex about 2 weeks ago (condom was used) for the first time in 6 months. AF was suppose to the 30th but came Wednesday night or so I thought. It's usually really heavy the first day but it wasn't and it's been mostly old blood it's not exactly light but it's not normal. I've read on here about implantation bleeding and everyone says 6-12 days after and it started exactly 12 days after. I've been really emotional and stressed is that why it's different? Could I be pregnant?