Thanks for writing in to us.
As you are already aware, the days during periods are relatively safe as far pregnancy
is concerned. It is indeed very unlikely for you to be pregnant. If the tampon was inside, the chances of any semen entering the vagina are almost nil.
Since you have mentioned the occurrence of irregular periods
, I suggest you wait until your next periods are due. If you do not get periods even 2 weeks after expected dates, then you may do the home pregnancy test by yourself.
Please have your boyfriend to use condoms. At 16 years you should not be taking unnecessary risks.
Hope this helps.