Uy congrats, mama! Based sa timeline mo, super possible na buntis ka na talaga, ang brownish spotting on day 13 ay maaaring implantation bleeding (usually happens 6-12 days after ovulation), at if the blood serum test came back positive, that's a strong sign na may buhay na! A few of us mums got positive results around similar timings, kaya I'd say go get an ultrasound with your OB para ma-confirm talaga and ma-ease your mind, lalo na kailangan mo ng clearance para sa vaccination mo. Congrats ulit, sana smooth ang journey mo!