Less than a day ago my significant other and i were in the shower and he came onto my chest, i am on birth control but is it possible to get pregnant?

No: Pregnancy under those conditions is very unlikely.

No worries: Salmon swim upstream to the same area where they hatched. Sperm are so small that you can't even see one with a magnifying glass. Being in the shower means the water is coming down from above, at 2 gallons per minute, unless it's one of those fancy Jacuzzi showers with water going sideways. Anyway, sperm are not salmon and cannot swim upriver to migrate into a vagina for spawning. No worries.