Not sure I belong here?

My daughter is 17 months old, and I never had a period again. I'm pregnant again (We wanted our children close in age) and I can only guess how far along I am? I had what I thought MIGHT be implantation bleeding on the 7th/8th, and I had a negative test about 2 or 3 weeks before that. I had been testing once or twice a month for a while because I simply hadn't had a period in so long.

Long story short: glow asked for my last period and it was in Sept 2015, lol. If ovulation/implantation occurred in late Nov/early October, can I safely assume I'll have a July baby or did I do the math wrong?