You wouldn't be feeling symptoms the day after or even a week after. Technically, you're not even pregnant until around 14 days after intercourse. It takes about 5-7 days for the sperm to make it to your tube, if there's an egg there, it takes another 5-7 days for that fertilized egg to get back down the uterus, implant and set off hormones. Until that point, you're not pregnant and have no symptoms. So your symptoms are likely a cold, flu, food poisoning or you psyching yourself out, not pregnancy. It's very unlikely that you're pregnant from that alone.
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Holly.
Mama to Hunter Kai