Is There Any Risk Of Pregnancy From Semen On My Underwear With No Penetration, Given That I Had A Normal Period 12 Days Later?

- On December 29th, my boyfriend ejaculated and I remember that one drop landed on my underwear. - I am pretty sure that I was not ovulating (my period came less than 12 days later so I counted back) - On January 2, there was only light blood but it did not look like any spotting. This persisted until the 5th. - On January 5th, I saw period blood on my pad and it was a normal, bright red flow. I am still having a regular flow. - No vaginal penetration occurred, but I still became a little anxious even though the circumstances above make pregnancy unlikely. Do you think I should be worried any longer?